Author name code: johansson
ADS astronomy entries on 2022-09-14
author:"Johansson, Sven-Eric" 
------------------------------------------------------------------------  

Title: VizieR Online Data Catalog: {eta} Car emission spectrum
    (1700-10400Å) (Zethson+, 2012)
Authors: Zethson, T.; Johansson, S.; Hartman, H.; Gull, T. R.
Bibcode: 2012yCat..35400133Z
Altcode: 2012yCat..35409133Z
  The spectra were recorded in a low state (March 1998) and an early
  high state (February 1999) with the Hubble Space Telescope/Space
  Telescope Imaging Spectrograph (HST/STIS) from 1640 to 10400Å using
  the 52"x0.1" aperture centered on Eta Carinae at position angle, PA=332
  degrees. Extractions of the reduced spectrum including both Weigelt B
  and D, 0.28" in length along the slit, were used to identify the narrow,
  nebular emission lines, measure their wavelengths and estimate their
  fluxes. <P />A linelist of 2500 lines is presented for the high and
  low states of the combined Weigelt blobs B and D. <P />(1 data file).

Title: η Carinae: linelist for the emission spectrum of the Weigelt
    blobs in the 1700 to 10 400 Å wavelength region
Authors: Zethson, T.; Johansson, S.; Hartman, H.; Gull, T. R.
Bibcode: 2012A&A...540A.133Z
Altcode:
  <BR /> Aims: We present line identifications in the 1700 to 10 400 Å
  region for the Weigelt blobs B and D, located 0″.1 to 0″.3 NNW of
  <ASTROBJ>Eta Carinae</ASTROBJ>. The aim of this work is to characterize
  the behavior of these luminous, dense gas blobs in response to the broad
  high-state and the short low-state of η Carinae during its 5.54-year
  spectroscopic period. <BR /> Methods: The spectra were recorded in a
  low state (March 1998) and an early high state (February 1999) with the
  Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS)
  from 1640 to 10 400 Å using the 52″ × 0″.1 aperture centered on
  Eta Carinae at position angle, PA = 332 degrees. Extractions of the
  reduced spectrum including both Weigelt B and D, 0″.28 in length along
  the slit, were used to identify the narrow, nebular emission lines,
  measure their wavelengths and estimate their fluxes. <BR /> Results:
  A linelist of 2500 lines is presented for the high and low states
  of the combined Weigelt blobs B and D. The spectra are dominated by
  emission lines from the iron-group elements, but include lines from
  lighter elements including parity-permitted and forbidden lines. A
  number of lines are fluorescent lines pumped by H Lyα. Other lines
  show anomalous excitation. <P />Table C.1 is also available at the
  CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
  href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/540/A133">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/540/A133</A>

Title: VUV oscillator strengths for iron lines of astrophysical
    importance
Authors: Hartman, H.; Nilsson, H.; Huldt, S.; Johansson, S.; Sörensen,
   S.; Johnson, M. S.; von Hessberg, P.
Bibcode: 2008JPhCS.130a2010H
Altcode:
  FeII lines are of great importance in analyses of stars and nebulae,
  not only for abundance studies, but also for diagnostics of the plasma
  conditions and derivation of physical properties such as temperature,
  electron density and radiation field. <P />We present a project where
  the ultimate goal is to derive transition rates for specific Fe II 4s
  — 5p transitions at VUV wavelengths. These are important for many
  astrophysical applications, e.g. in objects where line fluorescence is
  prominent as well as stars observed in the ultraviolet FUSE and HST/STIS
  region. In this wavelength region many other iron-group element ions
  have important transitions, which also will be measured. This work
  is performed as absorption measurements using a FeII hollow-cathode
  discharge, illuminated by synchrotron radiation at the MAX-lab facility
  (Lund, Sweden). The intensity ratio between absorption lines from a
  specific lower level can be determined, and transformed to an absolute
  scale using previously known f-values for a few lines. <P />We present
  results from low spectral resolution test runs on MAX-I, and outline the
  next step with its requirements for a high-resolution setup at MAX-III.

Title: Unidentified lines in the spectra of two iron overabundant
CP stars: are they FeII lines?
Authors: Castelli, F.; Johansson, S.; Hubrig, S.
Bibcode: 2008JPhCS.130a2003C
Altcode:
  The analysis of the high-resolution UVES spectra of the chemically
  peculiar stars HR6000 and 46 Aql has revealed the presence of an
  impressive number of unidentified lines, mostly concentrated in the
  regions 4404-4411 Å and 5100-5300 Å. Almost all of the unidentified
  lines are the same in both stars, which both have an iron abundance
  enhancement of the order of +0.7 dex over the solar value. The
  parameters adopted for HR 6000 and 46 Aql are T<SUB>eff</SUB>=12850 K,
  log g=4.1 and T<SUB>eff</SUB>=12750 K, log g=3.8, respectively. We show
  that some of the unknown lines can be identified as high-excitation
  (lower EP13eV) FeII and that most of them appear as unclassified lines
  in laboratory iron spectra.

Title: Precision Laboratory UV and IR Wavelengths for Cosmological
    and Astrophysical Applications
Authors: Aldenius, M.; Johansson, S.
Bibcode: 2008psa..conf..257A
Altcode: 2007astro.ph..3356A
  The quality of astronomical spectra is now so high that the accuracy
  of the laboratory data is getting more and more important. Both
  in astrophysics and in cosmology the needs for accurate laboratory
  wavelengths have increased with the development of new ground-based
  and air-borne telescopes and spectrographs. The high-resolution UV
  Fourier Transform (FT) spectrometer at Lund Observatory is being used
  for studying laboratory spectra of astrophysically important elements.

Title: Possibility of Heterodyne Correlation Interferometry with a
    Tunable Laser and Absolute Frequency Measurements
Authors: Johansson, S.; Letokhov, V.
Bibcode: 2008psa..conf..243J
Altcode:
  We consider the possibility of measuring the true width of the narrow
  optical spectral lines of astrophysical lasers. The lines should
  have a subDoppler spectral with of 30-100 MHz or even less. To make
  measurements with spectral resolution better than 10<SUP>7</SUP>
  and angular resolution better than 0.1 arcsec we suggest to use
  the ground-based Brown-Twiss-Townes optical heterodyne intensity
  correlation interferometry with the possibility of absolute frequency
  measurement. The estimates made of the S/N ratio for optical heterodyne
  astrophysical laser experiments imply that it should be feasible.

Title: Astrophysical lasers and nonlinear optical effects in space
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2007NewAR..51..443J
Altcode:
  The present state of the art concerning astrophysical lasers (APL)
  and nonlinear optical effects under astrophysical conditions is
  reviewed. The operational conditions of an APL (amplification
  under non-LTE conditions) and astrophysical predecessors of
  the laboratory lasers are considered in the introduction of the
  review. The rareness of observed APL action in the visible range in
  comparison with astrophysical masers (APM) in the microwave range
  is explained. Early proposals of APLs with collisional and optical
  pumping are discussed. APL/M in the mid-IR and submillimeter ranges
  linking APL and APM are also discussed. APLs in the Weigelt blobs of
  Eta Carinae operating in FeII and OI with a Bowen type optical pumping
  are considered in detail. General questions (narrowing of APL spectral
  lines, the possibility of scattering feedback and ways of measuring
  the true spectral width of an APL) are considered. Nonlinear optical
  effects in astrophysical conditions and resonance-enhanced two-photon
  conditions, in particular, are discussed in the conclusion.

Title: Accurate Ritz wavelengths of parity-forbidden [Fe II],
    [Ti II], and [Cr II] infrared lines of astrophysical interest
Authors: Aldenius, M.; Johansson, S.
Bibcode: 2007A&A...467..753A
Altcode: 2007astro.ph..3145A
  Context: With new astronomical infrared spectrographs the demands of
  accurate atomic data in the infrared have increased. In this region
  there is a large amount of parity-forbidden lines, which are of
  importance in diagnostics of low-density astrophysical plasmas. <BR
  />Aims: We present improved, experimentally determined, energy levels
  for the lowest even LS terms of Fe II, Ti II and Cr II, along with
  accurate Ritz wavelengths for parity-forbidden transitions between and
  within these terms. <BR />Methods: Spectra of Fe II, Ti II and Cr II
  have been produced in a hollow cathode discharge lamp and acquired using
  high-resolution Fourier Transform (FT) spectrometry. The energy levels
  have been determined by using observed allowed ultraviolet transitions
  connecting the even terms with upper odd terms. Ritz wavelengths of
  parity-forbidden lines have then been determined. <BR />Results: Energy
  levels of the four lowest Fe II terms (a<SUP>6</SUP>D, a<SUP>4</SUP>F,
  a<SUP>4</SUP>D and a<SUP>4</SUP>P) have been determined, resulting
  in 97 different parity-forbidden transitions with wavelengths between
  0.74 and 87 μm. For Ti II the energy levels of the two lowest terms
  (a<SUP>4</SUP>F and b<SUP>4</SUP>F) have been determined, resulting
  in 24 different parity-forbidden transitions with wavelengths between
  8.9 and 130 μm. Also for Cr II the energy levels of the two lowest
  terms (a<SUP>6</SUP>S and a<SUP>6</SUP>D) have been determined,
  in this case resulting in 12 different parity-forbidden transitions
  with wavelengths between 0.80 and 140 μm. <P />Tables 6-8 are only
  available in electronic form at http://www.aanda.org

Title: Experimental Mg I oscillator strengths and radiative lifetimes
    for astrophysical applications on metal-poor stars. New data for
    the Mg I b triplet
Authors: Aldenius, M.; Tanner, J. D.; Johansson, S.; Lundberg, H.;
   Ryan, S. G.
Bibcode: 2007A&A...461..767A
Altcode: 2006astro.ph.10033A
  Context: The stellar abundance ratio of Mg/Fe is an important
  tool in diagnostics of galaxy evolution. In order to make reliable
  measurements of the Mg abundance of stars, it is necessary to have
  accurate values for the oscillator strength (f-value) of each of the
  observable transitions. In metal-poor stars the Mg I 3p-4s triplet
  around 5175 Å (Fraunhofer's so-called b lines) are the most prominent
  magnesium lines. The lines also appear as strong features in the
  solar spectrum. <BR />Aims: We present new and improved experimental
  oscillator strengths for the optical Mg I 3p-4s triplet, along with
  experimental radiative lifetimes for six terms in Mg I. With these data
  we discuss the implications on previous and future abundance analyses
  of metal-poor stars. <BR />Methods: The oscillator strengths have been
  determined by combining radiative lifetimes with branching fractions,
  where the radiative lifetimes are measured using the laser induced
  fluorescence technique and the branching fractions are determined using
  intensity calibrated Fourier Transform (FT) spectra. The FT spectra
  are also used for determining new accurate laboratory wavelengths
  for the 3p-4s transitions. <BR />Results: The f-values of the Mg I
  3p-4s lines have been determined with an absolute uncertainty of 9%,
  giving an uncertainty of ± 0.04 dex in the log gf values. Compared
  to values previously used in abundance analyses of metal-poor stars,
  rescaling to the new values implies an increase of typically 0.04 dex
  in the magnesium abundance.

Title: New and improved experimental oscillator strengths in Zr II
    and the solar abundance of zirconium
Authors: Ljung, G.; Nilsson, H.; Asplund, M.; Johansson, S.
Bibcode: 2006A&A...456.1181L
Altcode:
  Using the Fourier Transform Spectrometer at Lund Observatory, intensity
  calibrated spectra of singly ionized zirconium have been recorded and
  analyzed. Oscillator strengths for 263 Zr II spectral lines in the
  region 2500-5400 Å have been derived by combining new experimental
  branching fractions with previously measured radiative lifetimes. The
  transitions combine 34 odd parity levels with 29 low metastable levels
  between 0 and 2.4 eV. The experimental branching fractions have been
  compared with theoretical values and the oscillator strengths with
  previously published data when available. The oscillator strengths
  have been employed to derive the solar photospheric Zr abundance
  based on both 1D and 3D model atmospheres. Based on the seven best
  and least perturbed Zr II lines in the solar disk-center spectrum, we
  determine the solar Zr abundance to log ɛ_Zr=2.58±0.02 when using a
  3D hydrodynamical solar model atmosphere. The new value is in excellent
  agreement with the meteoritic Zr abundance.

Title: Accurate laboratory ultraviolet wavelengths for quasar
    absorption-line constraints on varying fundamental constants
Authors: Aldenius, M.; Johansson, S.; Murphy, M. T.
Bibcode: 2006MNRAS.370..444A
Altcode: 2006MNRAS.tmp..601A; 2006astro.ph..5053A
  The most precise method of investigating possible
  space-time variations of the fine-structure constant, α ≡
  (1/ħc)(e<SUP>2</SUP>/4πɛ<SUB>0</SUB>), using high-redshift quasar
  absorption lines is the many-multiplet (MM) method. For reliable
  results this method requires very accurate relative laboratory
  wavelengths for a number of UV resonance transitions from several
  different ionic species. For this purpose laboratory wavelengths and
  wavenumbers of 23 UV lines from MgI, MgII, TiII, CrII, MnII, FeII and
  ZnII have been measured using high-resolution Fourier transform (FT)
  spectrometry. The spectra of the different ions (except for one FeII
  line, one MgI line and the TiII lines) are all measured simultaneously
  in the same FT spectrometry recording by using a composite hollow
  cathode as a light source. This decreases the relative uncertainties
  of all the wavelengths. In addition to any measurement uncertainty,
  the wavelength uncertainty is determined by that of the ArII
  calibration lines, by possible pressure shifts and by illumination
  effects. The absolute wavenumbers have uncertainties of typically
  +/-0.001-+/-0.002cm<SUP>-1</SUP> (Δ λ ~ 0.06-0.1mÅ at 2500Å),
  while the relative wavenumbers for strong, symmetric lines in the same
  spectral recording have uncertainties of +/- 0.0005 cm<SUP>-1</SUP>
  (Δλ ~ 0.03mÅ at 2500Å) or better, depending mostly on uncertainties
  in the line-fitting procedure. This high relative precision greatly
  reduces the potential for systematic effects in the MM method, while
  the new TiII measurements now allow these transitions to be used in
  MM analyses.

Title: Resonance-enhanced two-photon ionization (RETPI) of Si II
    and an anomalous, variable intensity of the λ1892 Si III] line in
    the Weigelt blobs of η Carinae
Authors: Johansson, S.; Hartman, H.; Letokhov, V. S.
Bibcode: 2006A&A...452..253J
Altcode: 2006astro.ph..2365J
  Context: .The Si III] 1892 Å intercombination line shows an anomalously
  high intensity in spectra of the radiation-rich Weigelt blobs in the
  vicinity of Eta Carinae. The line disappears during the 100 days long
  spectral events occurring every 5.5 years.<BR /> Aims: .The aim is to
  investigate whether resonance-enhanced two-photon ionization (RETPI)
  is a plausible excitation mechanism for the Si III] λ1892 line.<BR />
  Methods: .The possible intensity enhancement of the λ1892 line is
  investigated as regards quasi-resonant intermediate energy levels of
  Si II.<BR /> Results: .The RETPI mechanism is effective on Si II in
  the radiation-rich Weigelt blobs where the two excitation steps are
  provided by the two intense hydrogen lines Lyα and Lyγ.<BR />

Title: The nature of ultraviolet spectra of AG Pegasi and other
symbiotic stars: locations, origins, and excitation mechanisms of
    emission lines
Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M.
Bibcode: 2006A&A...451..157E
Altcode:
  A detailed study of ultraviolet spectra of the symbiotic star AG Peg has
  been undertaken to derive the atomic excitation mechanisms and origin
  of formation for the lines common in symbiotic systems. More than 600
  emission lines are observed in spectra from {IUE}, {HST} and {FUSE} of
  which 585 are identified. Population mechanisms and origin of formation
  are given for a majority of those lines. Based on the understanding
  of the AG Peg spectra {IUE} data of 19 additional symbiotic stars are
  investigated and differences and similarities of their spectra are
  discussed. Fe II fluorescence lines pumped by strong emission lines
  between 1000 and 2000 Å are observed in 13 of these systems. Some of
  the symbiotic systems belonging to the subclass symbiotic novae have
  more than 100 Fe II fluorescence lines in the ultraviolet wavelength
  region. Forbidden lines are detected for 13 of the stars, mostly
  from highly-ionized spectra such as Ar V, Ne V and Mg V. Further,
  [Mg VI] and [Mg VII] lines are observed in a symbiotic star (AG Dra)
  for the first time. Five of the symbiotic stars have broad white-dwarf
  wind profiles ({FWHM} &gt; 400 km s<SUP>-1</SUP>) for a few lines in
  their spectra. The stars with no such broad lines can be divided into
  two similarly sized groups, one where all lines have FWHM less than 70
  km s<SUP>-1</SUP> and the other where one, a few or all of the broad
  ({FWHM} &gt; 400 km s<SUP>-1</SUP>) lines of AG Peg have an enhanced
  broad wing (110-140 km s<SUP>-1</SUP>).

Title: Astrophysical laser operating in the OI 8446-Åline in the
    Weigelt blobs of η Carinae
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2005MNRAS.364..731J
Altcode: 2005MNRAS.tmp..964J
  Within the framework of a simple model of photophysical processes in
  the Weigelt blobs in the vicinity of the luminous blue variable (LBV)
  star η Carinae, we explain the presence of the fluorescent &lt;OI&gt;
  8446-Åand forbidden [OI] 6300-Ålines as well as the absence of
  the allowed OI 7774-Åline in spectra recorded with the Hubble Space
  Telescope (HST)/STIS instrument (Gull et al.). From atomic data and
  estimated stellar parameters we demonstrate that there is a population
  inversion and stimulated emission in the 3p<SUP>3</SUP>P-3s<SUP>3</SUP>S
  transition λ8446 due to photoexcitation by accidental resonance (PAR)
  by H Lyβ radiation.

Title: Bowen excitation of O III and N III in symbiotic stars
Authors: Eriksson, M.; Wahlgren, G. M.; Johansson, S.
Bibcode: 2005AAS...207.1302E
Altcode: 2005BAAS...37.1173E
  When ions in a plasma are subjected to emission lines very close in
  photon energy to the energy difference between two levels in the ions,
  the photons can pump the ions through the corresponding channel. This
  is called photoexcitation by accidental resonance (PAR). The most
  famous example of PAR is the Bowen mechanism, where the He II Lyα
  line at 303.783 Å pumps two 2p<SUP>2</SUP> - 2p3d channels in O III,
  at 303.800 and 303.695 Å, resulting in the so called O III Bowen
  lines between 2800 and 4000 Å. In IUE spectra of 20 symbiotic stars
  we observe the O III Bowen lines in 16. The O III Bowen lines are
  analyzed and the pumping efficiencies are discussed. In spectra of
  four of the symbiotic stars, AG Peg, RR Tel, HM Sge and V1016 Cyg, we
  observethe N III 3s-3p lines at 4000 Å and the 3p-3d lines at 4640 Å
  are observed. It was proposed already by Bowen (1935) that one of the
  O III lines, λ 374.432 could photoexcite N III through the channels
  at 374.434 and 374.442 Å, which would actually lead to the N III
  lines we observe in the symbiotic stars. We have modeled intensity
  ratios between the N III lines to test pumping by O III emission as
  the explanation for the N III 3s-3p and 3p-3d emission. This is valid
  for AG Peg but can be excluded for HM Sge. For RR Tel and V1016 Cyg
  the Bowen mechanism seems to be involved in the formation of the N
  III lines, but additional processes such as radiative recombination
  or charge-exchange with neutral hydrogen are needed to explain the
  observed intensity ratios.

Title: The FERRUM project: experimentally determined metastable
    lifetimes and transition probabilities for forbidden [TiII] lines
    observed in η Carinae
Authors: Hartman, H.; Schef, P.; Lundin, P.; Ellmann, A.; Johansson,
   S.; Lundberg, H.; Mannervik, S.; Norlin, L. -O.; Rostohar, D.;
   Royen, P.
Bibcode: 2005MNRAS.361..206H
Altcode: 2005MNRAS.tmp..563H
  In the spectrum of an emission-line region ejected from the massive star
  Eta Carinae, called the strontium filament (SrF), forbidden lines from
  many elements, in particular [SrII] and [TiII], are observed. These
  lines are strong in this specific region and valuable for plasma
  diagnostics. Forbidden lines are not easily produced in laboratory
  light sources and the atomic parameters for these lines can thus not
  be measured in a straightforward way. <P />We use a combination of
  laboratory and astrophysical measurements to determine transition
  probabilities for the [TiII] lines. Lifetimes for metastable levels
  in TiII are measured using a laser probing technique on a stored
  ion beam at CRYRING, MSL, Stockholm. Branching fractions from
  some of these levels are derived from Hubble Space Telescope/STIS
  spectra of the SrF. The astrophysical branching fractions are
  combined with the experimental lifetimes to determine absolute
  transition probabilities. <P />We report lifetimes for the TiII
  levels b<SUP>4</SUP>P<SUB>3/2</SUB>, b<SUP>2</SUP>P<SUB>1/2</SUB>,
  c<SUP>2</SUP>D<SUB>3/2</SUB> and c<SUP>2</SUP>D<SUB>5/2</SUB>,
  in the range 0.29-17 s, and transition probabilities for eight
  parity-forbidden lines from the levels c<SUP>2</SUP>D<SUB>3/2</SUB>
  and c<SUP>2</SUP>D<SUB>5/2</SUB>, along with uncertainty estimates.

Title: Time variations of the narrow Fe II and H I spectral emission
    lines from the close vicinity of η Carinae during the spectral
    event of 2003
Authors: Hartman, H.; Damineli, A.; Johansson, S.; Letokhov, V. S.
Bibcode: 2005A&A...436..945H
Altcode: 2005astro.ph..3410H
  The spectrum of <ASTROBJ>Eta Carinae</ASTROBJ> and its ejecta shows
  slow variations over a period of 5.5 years. However, the spectrum
  changes drastically on a time scale of days once every period called the
  "spectral event". We report on variations in the narrow emission line
  spectrum of gas condensations (the Weigelt blobs) close to the central
  star during a spectral event. The rapid changes in the stellar radiation
  field illuminating the blobs make the blobs a natural astrophysical
  laboratory to study atomic photoprocesses. The different responses of
  the HI Paschen lines, fluorescent &lt;Fe II&gt; lines and forbidden
  [Fe II] lines allow us to identify the processes and estimate physical
  conditions in the blobs. This paper is based on observations from the
  Pico dos Dias Observatory (LNA/Brazil) during the previous event in
  June 2003.

Title: Astrophysical Lasers in Optical Fe II Lines in Gas
    Condensations near η Carinae
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2005AIPC..770..399J
Altcode:
  We report here on the discovery of laser action in the range 0.9-2
  μm in several spectral lines of Fe II, which are associated with
  transitions from ``pseudo-metastable'' states populated by spontaneous
  transitions from Lyα pumped Fe II levels. The intense Lyα radiation
  is formed in the HII region of gas condensations close to the star η
  Car. The laser transitions form together with spontaneous transitions
  closed radiative cycles, one of which includes the extremely bright
  2507/09 Å lines. This fact, together with an accidental mixing of
  energy levels, may provide an explanation of the abnormal intensities of
  these UV non-lasing lines. Using the complicated energy level diagram of
  Fe II we present those peculiar features, which are essential for the
  inverted population and laser effect: the pumping, the level mixing,
  and the ``bottle neck'' for spontaneous decay. The laser action is a
  new indicator of non-equilibrium and spatially non-homogeneous physical
  conditions as well as a high brightness temperature of Lyα in ejecta
  from eruptive stars. Such conditions are very difficult to probe by
  existing methods.

Title: Metastable hydrogen absorption in ejecta close to η Carinae
Authors: Johansson, S.; Gull, T. R.; Hartman, H.; Letokhov, V. S.
Bibcode: 2005A&A...435..183J
Altcode:
  Spectroscopy with the high spatial resolution of the Hubble Space
  Telescope (HST) reveals narrow absorption in the hydrogen Balmer
  lines in spectra of Eta Carinae and the nearby nebular-scattered
  starlight. While hydrogen Balmer absorption lines are seen in stellar
  photospheres and winds, we are not aware of such being seen in
  galactic nebulae. This exceptional case is caused by intense stellar
  UV radiation acting on high-density neutral clumps of gas in the close
  vicinity of the central source. The interaction of the UV radiation
  with hydrogen results in photo-ionization and photo-excitation leading
  to a non-equilibrium population of the metastable 2s <SUP>2</SUP>S
  level. This occurs throughout the equatorial region surrounding η
  Carinae in sufficient quantity to produce strong narrow absorption
  on top of the broad P Cygni emission profile. This absorption can be
  considered to be a probe of the very non-uniform ejecta in the disk
  region surrounding η Carinae.

Title: Bowen excitation of N III lines in symbiotic stars
Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M.; Veenhuizen,
   H.; Munari, U.; Siviero, A.
Bibcode: 2005A&A...434..397E
Altcode:
  We present a semi-empirical equation for prediction of the strengths
  of those N III lines that are generated by the Bowen mechanism and
  observed in spectra of symbiotic stars. The equation assumes that the
  Bowen mechanism is the only source populating the 3d state in N III,
  and comparisons with observations of the 3s-3p and 3p-3d transitions
  serve as a test of this assumption. In an ongoing study of symbiotic
  stars the equation has been applied to two symbiotic novae, RR Tel and
  AG Peg, by comparing the predicted N III line strengths to observed
  line intensities. It is clear that besides the Bowen mechanism there is
  another process, most likely radiative recombination, that contributes
  to the N III 3d population in AG Peg and is the main population process
  of this state in RR Tel. It is also clear that a second, not previously
  considered, N III channel, 2p <SUP>2</SUP>P{1/2}-3d <SUP>2</SUP>D{3/2}
  at 374.198 Å, is pumped by O III in both RR Tel and AG Peg.

Title: Possibility of measuring the width of narrow Fe II
    astrophysical laser lines in the vicinity of η Carinae by means of
    Brown-Twiss-Townes heterodyne correlation interferometry
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2005NewA...10..361J
Altcode: 2005astro.ph..1246J
  We consider the possibility of measuring the true width of the
  narrow Fe II optical lines observed in spectra of the Weigelt blobs
  in the vicinity of η Carinae. The lines originate as a result of
  stimulated amplification of spontaneous emission of radiation in
  quantum transitions between energy levels showing inverted population
  [Johansson, S., Letokhov, V., 2002. JETP Lett. 75 (10) 495; Johansson,
  S., Letokhov, V., 2003. Phys. Rev. Lett. 90 (1) 01110-1; Johansson,
  S., Letokhov, V., 2004. A&amp;A 428,497]. The lines should have a
  subDoppler spectral width of 30-100 MHz, depending on the geometry of
  the lasing volume. To make measurements with a spectral resolution of
  R &gt; 10<SUP>7</SUP> and an angular resolution better than 0.1″, we
  suggest the use of the Brown-Twiss-Townes optical heterodyne intensity
  correlation interferometry. The estimates made of the S/N ratio for
  the optical heterodyne astrophysical laser experiment imply that it
  is feasible.

Title: Experimental Oscillator Strengths for Forbidden Lines in
    Complex Spectra
Authors: Hartman, H.; Johansson, S.; Lundberg, H.; Lundin, P.;
   Mannervik, S.; Schef, P.
Bibcode: 2005PhST..119...40H
Altcode:
  In dilute astrophysical plasmas, such as planetary nebulae and H II
  regions, strong lines appear that only have weak, if any, correspondence
  to the spectrum of laboratory light sources. Some of these are parity
  forbidden lines, i.e. emission from long-lived metastable states that
  cannot decay via normal electric dipole (E1) routes but only via the
  slower M1 and E2 transitions. The long lifetime of the upper levels
  and their sensitivity to collisions make the lines good diagnostics
  of the emitting plasma, but then the transition probability, or
  A-value, of these lines must be known. <P />We report on a technique
  to experimentally determine A-values for forbidden lines using
  the method of combining the lifetime of the upper level with the
  branching fractions for the different decay channels. The lifetime
  is measured using the laser probing technique (LPT) on a stored ion
  beam. Since these lines are rarely produced in laboratory plasmas,
  we use astrophysical spectra to determine the branching fractions
  (BF). The lifetime and the BF then give the A-value, which is one
  quantity needed for modeling the spectrum of the plasma emitting the
  forbidden lines. <P />The present measurements are performed within the
  FERRUM project, an international collaboration producing and evaluating
  transition probabilities for iron group element lines of astrophysical
  importance (Johansson P I S et al 2002 Physica Scripta T100 71)

Title: Stimulated Amplification under Spatially Nonhomogeneous
Conditions: An Astrophysical Fe II Laser in the Vicinity of Eta
    Carinae
Authors: Johansson, S.; Letokhov, V.
Bibcode: 2005PhST..120...99J
Altcode:
  We consider the conditions necessary for the development of an inverted
  population among the energy levels of free atoms in a medium exposed
  to radiation in spectral non-equilibrium. In particular, we focus
  on monochromatic radiation occurring as a result of an accidental
  wavelength coincidence between a pumping emission line and a pumped
  absorption line in two different elements. We examine especially
  the influence of `pseudo-metastable' states (at medium excitation)
  in the complex spectrum of Fe II, which cause a `bottleneck' in the
  radiative decay leading to an inverted level population. We also
  discuss the effect of `spectral compression' of the Lyman continuum
  into HLyα radiation at a high effective temperature. In conclusion
  we describe those differences between microwave astrophysical masers
  (APM) and optical astrophysical lasers (APL) that make the latter a
  more rare phenomenon in Nature.

Title: Astrophysical lasers operating in optical Fe II lines in
    stellar ejecta of η Carinae
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2004A&A...428..497J
Altcode: 2004astro.ph..9069J
  After the discovery of space masers based on OH radicals (Weaver et
  al. \cite{Wea65}) and H<SUB>2</SUB>O (Cheung et al. \cite{Che69}) such
  microwave lasers have been found to work in more than 100 molecular
  species (Elitzur \cite{Eli92}; Townes \cite{Tow97}), as well as in
  highly excited H atoms (Strelnitski et al. \cite{Str96}). In the IR
  region (10 \mum), the effect of stimulated emission of radiation in the
  CO<SUB>2</SUB> molecule has been discovered in the Martian and Venus'
  atmospheres (Betz et al. \cite{Bet76}; Mumma et al. \cite{Mum81}). We
  report here on the discovery of laser action in the range 0.9-2 μm in
  several spectral lines of Fe II, which are associated with transitions
  from ``pseudo-metastable'' states populated by spontaneous transitions
  from Lyα pumped Fe II levels. The intense Lyα radiation is formed
  in the HII region of gas condensations close to the star η Car. The
  laser transitions form together with spontaneous transitions closed
  radiative cycles, one of which includes the extremely bright 2507/09 Å
  lines. Closed radiative cycles, together with an accidental mixing of
  energy levels, may provide an explanation of the abnormal intensities of
  these UV non-lasing lines. Using the complicated energy level diagram of
  Fe II we present those peculiar features, which are essential for the
  inverted population and laser effect: the pumping, the level mixing,
  and the ``bottle neck'' for spontaneous decay. The laser action is a
  new indicator of non-equilibrium and spatially non-homogeneous physical
  conditions as well as a high brightness temperature of Lyα in ejecta
  from eruptive stars. Such conditions are very difficult to probe by
  existing methods, and we propose some future experiments. The fact,
  that the lasing near-IR lines appear in the spectrum with about the
  same intensity as non-lasing lines is discussed and compared with the
  situation in masers.

Title: Fe II Diagnostic Tools for Quasars
Authors: Verner, E.; Bruhweiler, F.; Verner, D.; Johansson, S.;
   Kallman, T.; Gull, T.
Bibcode: 2004ApJ...611..780V
Altcode: 2004astro.ph..4593V
  The enrichment of Fe relative to α-elements such as O and Mg represents
  a potential means to determine the age of quasars and probe the galaxy
  formation epoch. To explore how Fe II emission in quasars is linked to
  physical conditions and abundance, we have constructed an 830 level Fe
  II model atom and investigated through photoionization calculations
  how Fe II emission strengths depend on nonabundance factors. We have
  split Fe II emission into three major wavelength bands, Fe II (UV),
  Fe II (Opt1), and Fe II (Opt2), and explore how the Fe II (UV)/Mg
  II, Fe II (UV)/Fe II (Opt1), and Fe II (UV)/Fe II (Opt2) emission
  ratios depend on hydrogen density and ionizing flux in the broad-line
  regions (BLRs) of quasars. Our calculations show that (1) similar Fe II
  (UV)/Mg II ratios can exist over a wide range of physical conditions,
  (2) the Fe II (UV)/Fe II (Opt1) and Fe II (UV)/Fe II (Opt2) ratios
  serve to constrain ionizing luminosity and hydrogen density, and (3)
  flux measurements of Fe II bands and knowledge of the ionizing flux
  provide tools to derive distances to BLRs in quasars. To derive all
  BLR physical parameters with uncertainties, comparisons of our model
  with observations of a large quasar sample at low redshift (z&lt;1)
  are desirable. The STIS and NICMOS instruments aboard the Hubble Space
  Telescope offer the best means to provide such observations.

Title: Fe II fluorescence in symbiotic stars
Authors: Eriksson, M.; Veenhuizen, H.; Wahlgren, G. M.; Johansson, S.
Bibcode: 2004RMxAC..21..132E
Altcode: 2004IAUCo.191..132E
  Fe 0 fluorescence by PAR has been investigated in eight symbiotic
  stars having a wide range in temperature of the hot component and
  orbital period. The data used are spectra obtained from the IUE
  archive. All pumping lines investigated in this work are in the
  short wavelength region of IUE (1200-2000 Å), except for He 0 λ
  1084.942 and O 0 λ 1032.041. The resulting Fe 0 fluorescence lines
  are mainly in the long wavelength region (2000-3300 Å), but a few fall
  in the same region as the pumping lines. The aim is to understand the
  optimal conditions for formation of Fe 0 fluorescence lines caused by
  PAR. Three of the selected systems, RR Tel, AG Peg and V1016 Cyg, have
  10-30 active Fe 0 channels. Two conditions connect those systems to
  each other: The hot component is a white dwarf of extreme temperature
  (80 . 10<SUP>3</SUP>-150 . 10<SUP>3</SUP> K) and all three systems
  are so called symbiotic novae and have had outbursts during the last
  150 years. Three systems, AG Dra, RW Hya and R Aqr, have only 2-3
  active Fe 0 channels. In the two remaining systems, CI Cyg and T CrB,
  Fe 0 fluorescence lines were totally absent. These two systems have two
  features in common: The emission strength of highly ionized elements is
  less than in most symbiotic systems, and the hot component is suspected
  to be an accreting main sequence star rather than a white dwarf.

Title: Modeling the wind structure of AG Peg by fitting of C IV and
    N V resonance doublets
Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M.
Bibcode: 2004A&A...422..987E
Altcode:
  The latest outburst of AG Peg has lasted for 150 years, which makes
  it the slowest nova eruption ever recorded. During the time of IUE
  observations (1978-1995) line profiles and intensity ratios of the N V
  and C IV doublet components changed remarkably, and we discuss plausible
  reasons. One of them is radiative pumping of Fe II which is investigated
  by studying the fluorescence lines from pumped levels. Three Fe II
  channels are pumped by C IV and one by N V. The pumping rates of those
  Fe II channels as derived by the modeling agree well with the strengths
  of the Fe II fluorescence lines seen in the spectra. We model the C
  IV and N V resonance doublets in IUE spectra recorded between 1978
  and 1995 in order to derive optical depths, expansion velocities,
  and the emissivities of the red giant wind, the white dwarf wind and
  their collision region. The derived expansion velocities are ∼60 km
  s<SUP>-1</SUP> for the red giant wind and ∼700 km s<SUP>-1</SUP> for
  the white dwarf wind. We also suggest a fast outflow from the system
  at ∼150 km s<SUP>-1</SUP>. The expansion velocity is slightly higher
  for N V than for C IV. Emission from the collision region strongly
  affects the profile of the N V and C IV resonance doublets indicating
  its existence.

Title: Erratum: "Anomalous Fe II Spectral Effects and High H I Lyα
    Temperature in Gas Blobs Near η Carinae" [Astron. Lett. 30, 58
    (2004)]
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2004AstL...30..433J
Altcode:
  No abstract at ADS

Title: The Possibility of Resonance-Enhanced Two-Photon Ionization
    of Ne and Ar Atoms in Astrophysical Plasmas
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2004ARep...48..399J
Altcode:
  We consider possible schemes for the resonance-enhanced two-photon
  ionization (RETPI) of Ne and Ar atoms under the action of bichromatic
  radiation of intense resonance lines of HI, HeI, and HeII in a
  radiation-rich astrophysical plasma. The ionization rate is comparable
  to or exceeds the recombination rate in rarified astrophysical plasma,
  which leads to the accumulation of singly ionized ions with a subsequent
  transition to the higher ionization state via RETPI. We consider the
  RETPI reaction chains NeI → ... → NeV and ArI → ... → ArVI.

Title: Identification of emission lines in the low-ionization
    strontium filament near Eta Carinae
Authors: Hartman, H.; Gull, T.; Johansson, S.; Smith, N.; HST Eta
   Carinae Treasury Project Team
Bibcode: 2004A&A...419..215H
Altcode: 2004astro.ph..2489H
  We have obtained deep spectra from 1640 to 10 100 Å with the Space
  Telescope Imaging Spectrograph (STIS) of the strontium filament, a
  largely neutral emission nebulosity lying close to the very luminous
  star Eta Carinae and showing an uncommon spectrum. Over 600 emission
  lines, both permitted and forbidden, have been identified. The majority
  originates from neutral or singly-ionized iron group elements (Sc,
  Ti, V, Cr, Mn, Fe, Co, Ni). Sr is the only neutron capture element
  detected. The presence of Sr II, numerous strong Ti II and V II lines
  and the dominance of Fe I over Fe II are notable discoveries. While
  emission lines of hydrogen, helium, and nitrogen are associable with
  other spatial structures at other velocities within the Homunculus,
  no emission lines from these elements correspond to the spatial
  structure or velocity of the \ion{Sr} filament. Moreover, no
  identified \ion{Sr} filament emission line requires an ionization
  or excitation energy above approximately 8 eV. Ionized gas extends
  spatially along the aperture, oriented along the polar axis of the
  Homunculus, and in velocity around the strontium filament. We suggest
  that the strontium filament is shielded from ultraviolet radiation
  at energies above 8 eV, but is intensely irradiated by the central
  star at wavelengths longward of 1500 Å. <P />Based on observations
  made with the NASA/ESA Hubble Space Telescope, obtained at the Space
  Telescope Science Institute, which is operated by the Association
  of Universities for Research in Astronomy, Inc., under NASA contract
  NAS5-26555. <P />Tables 2 and 3 are only available in electronic form
  at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
  or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/419/215

Title: VizieR Online Data Catalog: Emission lines of Sr filament
    near {eta} Car (Hartman+, 2004)
Authors: Hartman, H.; Gull, T.; Johansson, S.; Smith, N.; HST Eta
   Carinae Treasury Project Team
Bibcode: 2004yCat..34190215H
Altcode:
  Spectral lines observed in the Sr-filament of {eta} Car in the
  wavelength region 2480-10140Å. The lines are sorted by wavelength in
  table 2 and sorted according to the periodic table in table 3. Both
  tables are available in postscript format as the file tables23.ps where
  the sub and superscripts for the atomic transitions are kept. <P />(3
  data files).

Title: Anomalous Fe II Spectral Effects and High H I Lyα Temperature
    in Gas Blobs Near η Carinae
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2004AstL...30...58J
Altcode:
  We consider the origin of the anomalously high intensity of the
  ultraviolet Fe II lambda 2507/2509 A lines observed with high spatial
  and spectral resolutions from gas blobs (GBs) near Carinae. This rare
  effect in stellar spectra is attributable to a combination of several
  factors: (1) the high hydrogen density (&gt;10^{8} cm^{-3}) that
  ensures the blocking of the Lyman continuum by GBs and, accordingly,
  the formation of a cold H I region with completely ionized Fe atoms;
  (2) the small distance between the GBs and the central star that
  ensures a high (&gt;8000-10 000 K) Ly_alpha H spectral temperature,
  which photoexcites Fe II selectively; and (3) the population of Fe II
  levels and, accordingly, the opening of a stimulated emission channel,
  which together with spontaneous transitions creates a radiative cycle
  where a single Fe II ion can multiply absorb Ly_alpha emission.

Title: Anomalously bright UV lines of Fe II as a probe of gas
    condensations in the vicinity of hot stars
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2003A&A...412..771J
Altcode:
  Two UV lines of Fe II at 2507/2509 Å are extremely bright in spatially
  resolved HST/STIS spectra of dense gas condensations (the so called
  Weigelt blobs) close to the central star of η Carinae. The lines
  also appear unresolved in HST/FOS spectra of the star AE And. Under
  normal conditions the lines should hardly be observable. Based on
  recent studies of the formation of the łambdałambda2507/2509 lines
  as part of a radiative cycle driven by HLyα pumping and including
  stimulated emission we propose the possibility of using them as a
  probe of non-homogeneities in gas condensations located outside hot,
  massive stars.

Title: Line absorption in the FUSE spectrum of the CP star 17 Com A
Authors: Wahlgren, G. M.; Ivarsson, S.; Johansson, S.; Proffitt, C. R.;
   Adelman, S. J.; Rice, J.; Gulliver, A. F.; Hill, G.; Leckrone, D. S.;
   Smith, D. P.
Bibcode: 2003AAS...203.9303W
Altcode: 2003BAAS...35.1358W
  We report on progress made in our Far Ultraviolet Spectroscopic Explorer
  (FUSE) program (ID A130; PI J.Rice) that pertains to understanding the
  absorption line spectrum of the magnetic chemically peculiar B star
  17 Com A (HD108662). Spectral observations were made on ten occasions
  with the FUSE observatory over a five day interval in April 2001 for
  the purpose of studying temporal flux variations over the stellar
  rotational period of 5.07 days. These data will allow us to correlate
  the far-UV flux variations with elemental abundance variations over
  the stellar surface as mapped out by optical Doppler image mapping
  techniques. Complementing the FUSE data are high-resolution optical
  spectra obtained at the Nordic Optical Telescope and the McDonald
  Observatory. From the optical spectra we have determined the rotational
  velocity (v sin i = 17 km s<SUP>-1</SUP>) and chemical abundances. The
  iron-group elements are generally enriched by a factor of 10 relative
  to the solar values and as such, are responsible for a large part
  of the line absorption in the FUSE spectral region. Using synthetic
  spectrum techniques with the abundances derived from the optical region
  data and FUSE archival spectra of normal and non-magnetic CP stars,
  we can identify approximately two-thirds of the absorption features
  in the FUSE spectrum of 17 Com A. In particular, we have concentrated
  on contributions from the Cr II/III and Fe II/III spectra. Aspects
  of atomic spectroscopy are also being carried out with the FUSE
  spectra. New experimental oscillator strengths for 4d-4f transitions of
  Fe II observed at optical wavelengths are used in conjunction with the
  FUSE spectra of chemically normal B type stars to determine oscillator
  strengths for important Fe II 3d-4f transitions.

Title: Astrophysical Lasers with Radiation Pumping by Accidental
    Resonance
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2003PASP..115.1375J
Altcode:
  In this paper we consider a general problem of astrophysical lasers
  operating with optical pumping by accidental resonance (PAR) with
  strong spontaneous emission lines of other elements. The origin of
  population inversion and the coefficient of amplification due to the
  optical excitation of atoms (ions) by a four-level scheme with PAR are
  analyzed. We elucidate conclusively the question of the manifestation of
  astrophysical lasers in the optical region of the spectrum, which in
  principle differs from that of astrophysical masers in the microwave
  range.

Title: The HST Treasury Project on Eta Carinae
Authors: Davidson, K.; Ishibashi, K.; Gull, T. R.; Martin, J. C.;
   Humphreys, R. M.; Damineli, A.; Weis, K.; Stahl, O.; Hillier, D. J.;
   Corcoran, M.; Hamann, F.; Walborn, N.; Johansson, S.; Hartman, H.;
   Bautista, M.
Bibcode: 2003AAS...203.5805D
Altcode: 2003BAAS...35.1302D
  This program is valuable for a broad range of stellar and nebular
  astrophysics, as well as data processing techniques and instrument
  characteristics. While observing this object's mysterious 5.5-year
  cycle, we obtained data on several distinct, complex, unfamiliar
  classes of spectra which cannot be observed well elsewhere. The
  stellar wind parameters lie outside normal experience, the Weigelt
  ejecta produce narrow-line spectra unlike any other known object, and
  the other spectra are also unusual. Altogether our results pertain to
  stellar instabilities close to the Eddington limit, extreme stellar
  winds, unexplored nebular/atomic excitation processes, nebular gas
  dynamics, and instrument performance. <P />The project also represents
  an extreme application of HST spectroscopy. Since η Car and its ejecta
  are spatially, spectrally, and temporally complex, they require the best
  available performance of HST/STIS across its full wavelength range. Such
  observations will probably not be attainable again within the next 15
  years. They also require improved data processing techniques which we
  have developed, useful for HST/STIS programs on other objects. The
  Eta Car Treasury data archive will be pertinent to a variety of
  significant problems mentioned above -- not just η Carinae. (See
  a related poster concerning the Archive.) <P />Here we report that
  (1) the predicted event did indeed occur during May--July 2003; (2)
  we obtained the planned data; (3) they show numerous fascinating and
  difficult-to-explain phenomena; and (4) we sketch improved reduction
  routines to achieve maximum resolution with STIS/CCD data in general. We
  also show examples of the spectral structure and variations in Eta
  Carinae. <P />This project is supported by STScI grant GO-9420.

Title: Improved oscillator strengths and wavelengths for Os I and
    Ir I, and new results on early r-process nucleosynthesis
Authors: Ivarsson, S.; Andersen, J.; Nordström, B.; Dai, X.;
   Johansson, S.; Lundberg, H.; Nilsson, H.; Hill, V.; Lundqvist, M.;
   Wyart, J. F.
Bibcode: 2003A&A...409.1141I
Altcode:
  The radioactive decay of <SUP>238</SUP>U and <SUP>232</SUP>Th has
  recently been used to determine ages for some of the oldest stars in
  the Universe. This has highlighted the need for accurate observational
  constraints on production models for the heaviest r-process elements
  which might serve as stable references, notably osmium and iridium. In
  order to provide a firmer basis for the observed abundances, we have
  performed laser-induced fluorescence measurements and Fourier Transform
  Spectroscopy to determine new radiative lifetimes and branching
  fractions for selected levels in Os I and Ir I. From these data, we
  determine new absolute oscillator strengths and improved wavelengths for
  18 Os I and 4 Ir I lines. A reanalysis of VLT spectra of CS 31082-001
  and new results for other stars with Os and Ir detections show that (i):
  the lines in the UV and lambda 4260 Å yield reliable Os abundances,
  while those at lambda lambda 4135, 4420 Å are heavily affected by
  blending; (ii): the Os and Ir abundances are identical in all the stars;
  (iii): the heavy-element abundances in very metal-poor stars conform
  closely to the scaled solar r-process pattern throughout the range 56
  &lt;= Z &lt;= 77; and (iv): neither Os or Ir nor any lighter species
  are suitable as reference elements for the radioactive decay of Th
  and U. <P />Based in part on observations obtained with the Very Large
  Telescope of the European Southern Observatory at Paranal, Chile.

Title: Revisited Abundance Diagnostics in Quasars: Fe II/Mg II Ratios
Authors: Verner, E.; Bruhweiler, F.; Verner, D.; Johansson, S.;
   Gull, T.
Bibcode: 2003ApJ...592L..59V
Altcode: 2003astro.ph..6533V
  Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]
  and resonance emission line complex of Mg II at 2800 Å are prominent
  features in quasar spectra. The observed Fe II(UV)/Mg II emission ratios
  have been proposed as means to measure the buildup of the Fe abundance
  relative to that of the α-elements C, N, O, Ne, and Mg as a function
  of redshift. The current observed ratios show large scatter and no
  obvious dependence on redshift. Thus, it remains unresolved whether a
  dependence on redshift exists and whether the observed Fe II(UV)/Mg
  II ratios represent a real nucleosynthesis diagnostic. We have used
  our new 830 level model atom for Fe<SUP>+</SUP> in photoionization
  calculations, reproducing the physical conditions in the broad-line
  regions of quasars. This modeling reveals that interpretations of
  high values of Fe II(UV)/Mg II are sensitive not only to Fe and Mg
  abundance, but also to other factors such as microturbulence, density,
  and properties of the radiation field. We find that the Fe II(UV)/Mg
  II ratio combined with Fe II(UV)/Fe II(optical) emission ratio, where
  Fe II(optical) denotes Fe II emission in 4000-6000 Å band, can be
  used as a reliable nucleosynthesis diagnostic for the Fe/Mg abundance
  ratios for the physical conditions relevant to the broad-line regions
  of quasars. This has extreme importance for quasar observations with
  the Hubble Space Telescope and also with the future James Webb Space
  Telescope.

Title: Experimental f-Value and Isotopic Structure for the Ni I Line
    Blended with [O I] at 6300 Å
Authors: Johansson, S.; Litzén, U.; Lundberg, H.; Zhang, Z.
Bibcode: 2003ApJ...584L.107J
Altcode: 2003astro.ph..1382J
  We have measured the oscillator strength of the Ni I line at 6300.34
  Å, which is known to be blended with the forbidden line [O I]
  λ6300 used for the determination of the oxygen abundance in cool
  stars. We also give wavelengths of the two isotopic line components
  of <SUP>58</SUP>Ni and <SUP>60</SUP>Ni derived from the asymmetric
  laboratory line profile. These two line components of Ni I have to
  be considered when calculating a line profile of the 6300 Å feature
  observed in stellar and solar spectra. We also discuss the labeling of
  the energy levels involved in the Ni I line since level mixing makes
  the theoretical predictions uncertain.

Title: The FERRUM Project: Experimental transition probabilities  of
    [Fe II] and astrophysical applications
Authors: Hartman, H.; Derkatch, A.; Donnelly, M. P.; Gull, T.;
   Hibbert, A.; Johansson, S.; Lundberg, H.; Mannervik, S.; Norlin,
   L. -O.; Rostohar, D.; Royen, P.; Schef, P.
Bibcode: 2003A&A...397.1143H
Altcode:
  We report on experimental transition probabilities for thirteen
  forbidden [Fe II] lines originating from three different metastable Fe
  Ii levels. Radiative lifetimes have been measured of two metastable
  states by applying a laser probing technique on a stored ion
  beam. Branching ratios for the radiative decay channels, i.e. M1
  and E2 transitions, are derived from observed intensity ratios
  of forbidden lines in astrophysical spectra and compared with
  theoretical data. The lifetimes and branching ratios are combined to
  derive absolute transition probabilities, A-values. <P />We present
  the first experimental lifetime values for the two Fe II levels
  a<SUP>4</SUP>G<SUB>9/2</SUB> and b<SUP>2</SUP>H<SUB>11/2</SUB> and
  A-values for 13 forbidden transitions from a<SUP>6</SUP>S<SUB>5/2</SUB>,
  a<SUP>4</SUP>G<SUB>9/2</SUB> and b<SUP>4</SUP>D<SUB>7/2</SUB> in the
  optical region. A discrepancy between the measured and calculated
  values of the lifetime for the b<SUP>2</SUP>H<SUB>11/2</SUB> level
  is discussed in terms of level mixing.\ We have used the code CIV3 to
  calculate transition probabilities of the a<SUP>6</SUP>D-a<SUP>6</SUP>S
  transitions. <P />We have also studied observational branching ratios
  for lines from 5 other metastable Fe II levels and compared them to
  calculated values. A consistency in the deviation between calibrated
  observational intensity ratios and theoretical branching ratios for
  lines in a wider wavelength region supports the use of [Fe II] lines
  for determination of reddening.

Title: Temporal Variations of Fe II Fluorescence Lines in the
    Symbiotic Star AG Peg
Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M.
Bibcode: 2003ASPC..303..109E
Altcode: 2003ssps.conf..109E
  No abstract at ADS

Title: Radiative Cycle with Stimulated Emission from Atoms and Ions
    in an Astrophysical Plasma
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2003PhRvL..90a1101J
Altcode: 2002astro.ph.12382J
  We propose that a radiative cycle operates in atoms and ions located
  in a rarefied gas in the vicinity of a hot star. Besides spontaneous
  transitions the cycle includes a stimulated transition in one very
  weak intermediate channel. This radiative “bottleneck” creates a
  population inversion, which for an appropriate column density results
  in amplification and stimulated radiation in the weak transition. The
  stimulated emission opens a fast decay channel leading to a fast
  radiative cycle in the atom (or ion). We apply this model by explaining
  two unusually bright FeII lines at 250.7 and 250.9nm in the UV spectrum
  of gas blobs close to η Carinae, one of the most massive and luminous
  stars in the Galaxy.

Title: Comments on atomic data for the GAIA spectral region
Authors: Wahlgren, G. M.; Johansson, S.
Bibcode: 2003ASPC..298..481W
Altcode: 2003gsst.conf..481W
  No abstract at ADS

Title: The -145 km/s Absorption System of Eta Carinae
Authors: Vieira, G. L.; Gull, T. R.; Danks, A. C.; Johansson, S.
Bibcode: 2002AAS...201.4904V
Altcode: 2002BAAS...34.1184V
  With the STIS E230H mode (R 118,000), we have identified about twenty
  absorption components in line of sight from Eta Carinae. Two components,
  one at -513 km/s and another at -145 km/s, are quite different in
  character from the others, mostly at intermediate velocities (See
  adjacent posters by T. Gull and A. Danks). The -145 km/s component
  is significantly wider in fwhm, is seen in many more species, and
  the lower level can be above 20,000 cm-1, well above the 2000 cm-1
  noted in the -513 km/s component. In the spectral region from 2400 to
  3160A, approximately 500 absorption lines have been identified. In this
  poster, we will present line identifications and atomic parameters of
  the measured lines, hopefully providing insight as to what levels are
  being excited and by what processes. Observations were accomplished
  through STScI under proposal 9242 (Danks, P.I.). Funding is through
  the STIS GTO resources.

Title: Properties of the -513 km/s Ejecta in the Spectrum of Eta
    Carinae
Authors: Danks, A. C.; Gull, T. R.; Vieira, G. L.; Johansson, S.
Bibcode: 2002AAS...201.4905D
Altcode: 2002BAAS...34.1184D
  In the spectral region 2400-3160A of Eta Carinae, we have identified
  approximately 500 absorption lines each with up to twenty velocity
  components.The -512 km/s component is truely unique as 1) the typical
  line width is &lt;3 km/s, 2) the identified lines are in Fe I, Fe II,
  V II and Ti II, and 3) the lines originate from lower levels up to 2000
  cm-1 above the ground level. We have measured the velocity centers,
  full width at half maximum and equivalent widths for approximately
  100 absorption lines. Initial results were very confusing as we
  found more variation in central velocities than would be expected
  from known STIS echelle wavelength standards. Upon further review, we
  found that the reporteded wavelengths in the NIST and Kurucz databases
  were not sufficiently accurate. S. Johansson searched FTS laboratory
  measurements performed at Lund for V II and Ti II and provided much
  improved wavelength measures. Likewise, we find more variation in
  column density than expected statistically from the accuracy of the
  equivalent widths for lines originating from the same energy level. We
  are reviewing the published gf values and our measurements to improve
  the measured column densities. Some spectroscopy of the ejecta
  has already been accomplished at two different epochs. Preliminary
  measures of equivalent widths indicate there may be some variation
  with time, but we await measurements planned for July 2003 during the
  upcoming spectroscopic minimum of Eta Carinae. These observations were
  accomplished through STScI and funding was from STIS GTO resources.

Title: The FERRUM Project: Experimental oscillator strengths of
    the UV 8 multiplet and other UV transitions from the y<SUP>6</SUP>P
    levels of Fe II
Authors: Pickering, J. C.; Donnelly, M. P.; Nilsson, H.; Hibbert,
   A.; Johansson, S.
Bibcode: 2002A&A...396..715P
Altcode:
  We report on experimental branching fractions (BFs) for 19 transitions
  from the three 3d<SUP>5</SUP>(<SUP>6</SUP>S)4s4p(<SUP>3</SUP>P)
  y<SUP>6</SUP>P levels in Fe II, measured in Fourier transform spectra
  of a Penning discharge lamp and a hollow cathode lamp. The transition
  wavelengths span the interval between 1600 and 2850 Å. Absolute
  oscillator strengths (f-values) have been derived by combining
  the BFs with experimental radiative lifetimes recently reported
  in the literature. Theoretical f-values have been calculated using
  configuration interaction wavefunctions. The new experimental and
  theoretical f-values are compared with data available in the literature
  and in databases. The strongest lines measured belong to the UV 8
  multiplet of Fe II, which has one ground state transition appearing
  as a prominent feature at 1608 Å in interstellar spectra. The line
  is accompanied by a satellite at 1611 Å due to a level mixing, which
  is discussed in the paper.

Title: The Origin of Fe II and [Fe II] Emission Lines in the
    4000-10000 Å Range in the BD Weigelt Blobs of η Carinae
Authors: Verner, E. M.; Gull, T. R.; Bruhweiler, F.; Johansson, S.;
   Ishibashi, K.; Davidson, K.
Bibcode: 2002ApJ...581.1154V
Altcode:
  We present numerical simulations that reproduce the salient features of
  the amazingly strong [Fe II] and Fe II emission spectra in the B and
  D Weigelt blobs of η Carinae. For our studies we have used spectra
  obtained during the 1998 epoch observations with the Hubble Space
  Telescope (HST). The spectrum of the B and D Weigelt blobs dominates in
  [Fe II] and Fe II emission lines. The same observations show no Fe I or
  Fe III. We have compared our measurements of the strongest (&gt;=200)
  [Fe II] and Fe II lines and blends in the spectrum with theoretical
  predictions. Our predictions are based on non-LTE modeling of the Fe II
  atom, which includes the lowest 371 energy levels (all levels up to 11.6
  eV). We have investigated the dependence of the spectrum on electron
  density, pumping by the blackbody-like stellar continuum, and intense
  Lyα emission. We find that radiative pumping is essential in explaining
  the observed spectrum. We have identified the main pumping routes
  responsible for the observed Fe II emission. Comparison between the
  model and observations reveals details of the radiation field. Pumping
  by the blackbody-like stellar radiation field from η Carinae explains
  the numerous strong [Fe II] and Fe II lines in the range of 4000-6500
  Å. The strongest Fe II lines in a range of 8000-10000 Å are pumped by
  intense Lyα radiation. Based on observations made with the NASA/ESA
  Hubble Space Telescope, obtained at the Space Telescope Science
  Institute, which is operated by the Association of Universities for
  Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Title: Erratum: Successsive resonance-enhanced two-photon ionization
    of elements abundant in nebulae. I. Atoms and ions of C, N, and O
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2002A&A...395..345J
Altcode:
  No abstract at ADS

Title: The origin of the anomalous intensity ratio between very
    bright UV FeII lines and their satellites in gaseous condensations
    close to the star eta Carinae
Authors: Klimov, V.; Johansson, S.; Letokhov, V. S.
Bibcode: 2002A&A...385..313K
Altcode:
  We present a model that explains the anomalous intensity ratios
  between each of two very bright UV lines of Fe II at 2507 Å and 2509
  Å and its corresponding satellite line, observed in HST spectra
  of a compact gaseous condensation (blob B) in the vicinity of the
  star protect eta Car.The model is based on the assumption that the
  FeII transitions have a substantial optical thickness, which varies
  as a result of the photodepletion of the long-lived lower states,
  c<SUP>4</SUP>F<SUB>7/2,9/2</SUB>, by the intense Lyalpha radiation. In
  conditions where the photodepletion rates of these two states differ,
  the resonance scattering lengths of the spectral lines become different
  as well. In the presence of a weak, nonresonant (continuous) absorption,
  this gives rise to a difference in attenuation between the spectral
  lines (the Hummer effect (Hummer 1968)). It is the combination of
  these two effects that explains the anomalous (as compared with
  laboratory data) intensity ratios observed in the two pairs of UV
  FeII lines. Ionization channels of stimulated photodepletion by the
  Lyalpha radiation, including the possible role of autoionization levels,
  are considered.

Title: Experimental oscillator strengths in U II of cosmological
    interest
Authors: Nilsson, H.; Ivarsson, S.; Johansson, S.; Lundberg, H.
Bibcode: 2002A&A...381.1090N
Altcode:
  Oscillator strengths for 57 U II lines in the region 3500-6700 Å have
  been derived by combining new branching fraction measurements with
  recently measured lifetimes. The lines combine six upper levels with
  numerous low levels having excitation energies of 0-1.5 eV. The data
  include the U II line at 3859 Å, which is used for cosmochronology.

Title: The FERRUM Project: New f-value Data for Fe II and
    Astrophysical Applications
Authors: Johansson, S.; Derkatch, A.; Donnelly, M. P.; Hartman, H.;
   Hibbert, A.; Karlsson, H.; Kock, M.; Li, Z. S.; Leckrone, D. S.;
   Litzén, U.; Lundberg, H.; Mannervik, S.; Norlin, L. -O.; Nilsson,
   H.; Pickering, J.; Raassen, T.; Rostohar, D.; Royen, P.; Schmitt,
   A.; Johanning, M.; Sikström, C. M.; Smith, P. L.; Svanberg, S.;
   Wahlgren, G. M.
Bibcode: 2002PhST..100...71J
Altcode:
  We present the FERRUM Project, an international collaboration aiming
  at a production and evaluation of oscillator strengths (transition
  probabilities) of selected spectral lines of singly ionized iron group
  elements, that are of astrophysical relevance. The results obtained
  include measurements and calculations of permitted and forbidden
  lines of Fe II. The data have been applied to both emission and
  absorption lines in astrophysical spectra. We make comparisons between
  experimental, theoretical and astrophysical f-values. We give a general
  review of the various measurements, and discuss the UV8 multiplet of
  Fe II around 1610 Å in detail.

Title: Experimental oscillator strengths in Th II
Authors: Nilsson, H.; Zhang, Z. G.; Lundberg, H.; Johansson, S.;
   Nordström, B.
Bibcode: 2002A&A...382..368N
Altcode:
  We have measured radiative lifetimes of ten Th II levels by using
  the laser-induced fluorescence technique and branching fractions
  with Fourier transform spectroscopy. By combining the new branching
  fractions with a total of 23 lifetimes, from the present work and from
  measurements by Simonsen et al. (\cite{Simonsen}), absolute oscillator
  strengths for 180 lines have been derived. Some of these new f-values
  reported are relevant for radioactive dating of stars.

Title: The Strontium Filament within the Homunculus of Eta Carinae
Authors: Gull, T. R.; Hartman, H.; Zethson, T.; Johansson, S.;
   Ishibashi, K.; Davidson, K.
Bibcode: 2001AAS...19913501G
Altcode: 2001BAAS...33R1505G
  During a series of HST/STIS observations of Eta Carinae and associated
  ejecta, we noticed a peculiar emission filament located a few arcseconds
  north of the central source. While bright in nebular standards, it
  is submerged in a sea of scattered starlight until moderately high
  dispersion, long-slit spectroscopy with the STIS (R 8000) brings
  the emission lines out. The initial spectrum, centered on 6768A with
  the STIS G750M grating, led to identification of twenty lines from
  singly-ionized species including [Sr II], [Fe II], [Ti II], [Ni II],
  [Mn II], and [Co II] (Zethson, etal., 2001, AJ 122, 322). No Balmer
  emission is detected from this filament and the Fe II 2507,9 lines,
  known to be pumped by Lyman alpha radiation in other regions near the
  central source, are not detected. Followup observations have led to
  detection of hundreds more emission lines from iron group elements in
  neutral and singly-ionized states. Thus far all are excited by less
  than 10 eV. This peculiar nebular emission is thought to be due to
  very intense stellar radiation, stripped of uv flux shortward of Lyman
  alpha, bathing a neutral structure. We are systematically identifying
  the many lines (over 90% identified) and measuring line intensities
  that will then be modeled to determine excitation mechanisms,
  temperature and density. Two [Sr II] and two Sr II lines have now been
  measured. Bautista, etal. (in preparation) have modeled the strontium
  flux ratios and find that large radiation fluxes and/or high strontium
  abundances may account for the detected emission. These observations
  were supported by STIS GTO funding and GO funding through the STScI.

Title: A model for the origin of the anomalous and very bright UV
    lines of Fe II in gaseous condensations of the star η Carinae
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2001A&A...378..266J
Altcode:
  We present a qualitative physical model of the origin of two very
  bright UV lines of Fe II at 2507-2509 Å, present in high-resolution
  spectra of gaseous condensations (blobs) close to the central star
  of eta Carinae. The spectra have been obtained with the Hubble Space
  Telescope (HST). The model is based on a type of Bowen mechanism
  with selective photoexcitation of Fe II by a broad HLyalpha profile,
  generated in the HII region and diffusely transferred to the optically
  thick HI region. The frequency distribution by large Doppler diffusion
  into the HI region provides a substantial broadening of HLyalpha ,
  which makes it possible to selectively photo-excite short-lived
  (~1 ns) states at 11.2 eV in Fe II. Within the frame of the present
  model the intense HLyalpha radiation induces a depletion of the lower,
  long-lived (~1 ms) level of the strong UV lines by photoionization. The
  subsequent recombination of Fe III explains the appearance of the
  ``forest'' of narrow Fe II lines. The possibility of a cyclic process
  is also discussed, where HLyalpha induces depletion to bound states,
  which have fast decays in the far-UV to the lower state of the Bowen
  pumping channel.

Title: The FERRUM project: Branching ratios and atomic transition
    probabilities of Fe II transitions from the 3d<SUP>6</SUP>(a
    <SUP>3</SUP>F)4p subconfiguration in the visible to VUV spectral
    region
Authors: Pickering, J. C.; Johansson, S.; Smith, P. L.
Bibcode: 2001A&A...377..361P
Altcode:
  We report measurements of the relative intensities of 81 emission
  lines of Fe II between 160 nm and 350 nm (62 168 cm<SUP>-1</SUP>
  to 28 564 cm<SUP>-1</SUP>) from 4 levels by high resolution Fourier
  transform spectrometry, using a Penning discharge lamp as light
  source. These relative intensities have been used to determine
  the line branching fractions, which have then been combined with
  accurate experimental radiative lifetime measurements reported
  recently to give absolute transition probabilities and oscillator
  strengths for 81 lines. The accuracy of these f-values is compared
  with other previous experimental measurements, and with theoretical
  values. The new transition probabilities will allow accurate
  determinations of Fe II abundances in a wide variety of astrophysical
  objects. Tables 2 and 3 are only available in electronic form at the
  CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
  http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/377/361

Title: Successsive resonance-enhanced two-photon ionization of
    elements abundant in nebulae. I. Atoms and ions of C, N, and O
Authors: Johansson, S.; Letokhov, V. S.
Bibcode: 2001A&A...375..319J
Altcode:
  We discuss resonance-enhanced two-photon ionization (RETPI) and
  present schemes of successive RETPI of the elements C, N, and O in
  nebulae. RETPI is activated by intrinsic radiation stored in the form
  of trapped spectral lines of HI, HeI, and HeII in the optically thick
  nebula. The rate of this two-step photoionization is comparable with
  or exceeds the low recombination rate of the photoions formed in the
  process. This leads to an accumulation of photoions and subsequent
  RETPI until such highly charged ions are formed that they cannot
  further be ionized in this way by the intrinsic radiation from the
  strong spectral lines of HI, HeI, and HeII.

Title: New laboratory lifetime measurements of U II for the uranium
    cosmochronometer
Authors: Lundberg, H.; Johansson, S.; Nilsson, H.; Zhang, Z.
Bibcode: 2001A&A...372L..50L
Altcode:
  We present new measurements of radiative lifetimes for
  six energy levels of singly ionized uranium, U II, using
  laser-induced fluorescence technique. One of the levels,
  5f<SUP>3</SUP>6d7p<SUP>6</SUP>M<SUB>13/2</SUB> at 26191 cm<SUP>-1</SUP>,
  decays by a transition at 3859.6 Å. This line has recently been
  observed in the spectrum of the metal-poor star CS1082-001, the
  first detection of uranium outside the solar system. The lambda 3859
  line can be used as the presently most accurate cosmochronometer
  (Cayrel et al. \cite{Cayrel}). Our value of the lifetime of the
  <SUP>6</SUP>M<SUB>13/2</SUB> level is 18.6+/-0.7 ns, and it confirms the
  f-value used in the Nature article by Cayrel et al. (\cite{Cayrel}),
  which is based on an experimental lifetime of 20+/-5 ns (Chen &amp;
  Borzileri \cite{Chen}). The new measurement also removes the doubt about
  the choice between that value and other f-values in the literature,
  differing by a factor of 3. Adopting the same branching fraction as
  Chen &amp; Borzileri (\cite{Chen}) for the 3859.6 Å line, we derive
  a gf-value of 0.68, which is 8% higher than the value used by Cayrel
  et al. (\cite{Cayrel}). Of significance for the chronometer is also
  the reduced uncertainty of the radiative lifetime, 4% compared to 25%,
  and consequently of the f-value, which should decrease the uncertainty
  in the determination of the stellar age considerably.

Title: The FERRUM project: Experimental f-values for 4p-5s transitions
    in Fe II
Authors: Karlsson, H.; Sikstrom, C. M.; Johansson, S.; Li, Z. S.;
   Lundberg, H.
Bibcode: 2001A&A...371..360K
Altcode:
  New measurements of radiative lifetimes of four 3d<SUP>6</SUP>5s levels
  in Fe II at about 10 eV are presented along with absolute oscillator
  strengths for twenty 4p-5s transitions involving the four levels. The
  experimental measurements are compared with two different sets of
  theoretical calculations. The lines are of particular interest in the
  modeling of HLyalpha pumped fluorescence of Fe II in astrophysical
  plasmas.

Title: The Bismuth Abundance in the HGMN Stars χ Lupi and HR 7775
    and Improved Atomic Data for Selected Transitions of BI I, BI II,
    and BI III
Authors: Wahlgren, G. M.; Brage, T.; Brandt, J. C.; Fleming,
   J.; Johansson, S.; Leckrone, D. S.; Proffitt, C. R.; Reader, J.;
   Sansonetti, C. J.
Bibcode: 2001ApJ...551..520W
Altcode:
  High-resolution spectra of the chemically peculiar HgMn stars χ Lupi
  and HR 7775, obtained with the Hubble Space Telescope/Goddard High
  Resolution Spectrograph, are investigated for their abundance of bismuth
  by comparison with LTE synthetic spectrum modeling. HR 7775, previously
  known from International Ultraviolet Explorer spectra to display strong
  lines of Bi II, is determined to have bismuth present at an enhancement
  level of nearly 5 orders of magnitude from the lines Bi II λλ1436,
  1902 and Bi III λ1423. The bismuth enhancement for χ Lupi is found
  to be near a level of 1.5 dex, and an ionization anomaly between
  Bi<SUP>+</SUP> and Bi<SUP>++</SUP> is apparent. HR 7775 abundance
  enhancements of the heavy elements platinum, [Pt/H]=4.7 dex, and gold,
  [Au/H]=3.8 dex, have also been determined. New laboratory measurements
  for wavelengths and hyperfine structure patterns of Bi I/Bi II/Bi
  III lines are presented, as well as the results of calculations for
  hyperfine structure constants and oscillator strengths for selected
  lines of Bi II and Bi III. Based on observations with the NASA/ESA
  Hubble Space Telescope, obtained at the Space Telescope Science
  Institute, which is operated by the Association of Universities for
  Research in Astronomy, Inc., under NASA contract NAS5-26555.

Title: Intensity anomalies in the C IV doublet caused by Fe II
    fluorescence
Authors: Eriksson, M.; Johansson, S.; Wahlgren, G.
Bibcode: 2001ASPC..242..325E
Altcode: 2001ecom.conf..325E
  No abstract at ADS

Title: Identification of Lines in the Strontium Region of Eta Carinae
Authors: Hartman, H.; Zethson, T.; Johansson, S.; Gull, T.; Ishibashi,
   K.; Davidson, K.; Smith, N.
Bibcode: 2001ASPC..242..107H
Altcode: 2001ecom.conf..107H
  No abstract at ADS

Title: Mysterious UV Lines of Fe II in the Blob Spectrum of Eta
    Carinae
Authors: Johansson, S.; Letokhov, V.
Bibcode: 2001ASPC..242..309J
Altcode: 2001ecom.conf..309J
  No abstract at ADS

Title: Fluorescence Lines in Eta Carinae and Other Objects
Authors: Johansson, S.; Zethson, T.; Hartman, H.; Letokhov, V.
Bibcode: 2001ASPC..242..297J
Altcode: 2001ecom.conf..297J
  No abstract at ADS

Title: Cr II Fluorescence in Eta Carinae due to H Lyman Alpha Pumping
Authors: Zethson, T.; Hartman, H.; Johansson, S.; Gull, T.; Ishibashi,
   K.; Davidson, K.
Bibcode: 2001ASPC..242...97Z
Altcode: 2001ecom.conf...97Z
  No abstract at ADS

Title: Fluorescence Observed in the Ultraviolet Spectrum of RR
    Telescopii
Authors: Hartman, H.; Johansson, S.
Bibcode: 2001ASPC..242..361H
Altcode: 2001ecom.conf..361H
  No abstract at ADS

Title: Accurate laboratory wavelengths of some ultraviolet lines
    of Cr, Zn and Ni relevant to time variations of the fine structure
    constant
Authors: Pickering, J. C.; Thorne, A. P.; Murray, J. E.; Litzén,
   U.; Johansson, S.; Zilio, V.; Webb, J. K.
Bibcode: 2000MNRAS.319..163P
Altcode:
  The quality of astronomical spectroscopic data now available is
  so high that interpretation and analysis are often limited by the
  uncertainties of the laboratory data base. In particular, the limit
  with which space-time variations in the fine structure constant α
  can be constrained using quasar spectra depends on the availability
  of more accurate laboratory rest wavelengths. We recently measured
  some transitions in magnesium by high-resolution Fourier transform
  spectroscopy for this purpose, and we now report measurements on some
  ultraviolet resonance lines of Znii (2062 and 2026Å), Crii (2066,
  2062 and 2056Å) and Niii (1751, 1741, 1709 and 1703Å). Apart from the
  last line, which is very weak, the uncertainty of these measurements
  is 0.002cm<SUP>-1</SUP> (0.08må) for the lines around 2000Å and
  0.004cm<SUP>-1</SUP> (0.12må) for the lines around 1700Å.

Title: The FERRUM project: new experimental and theoretical f-values
    for 4p-4d transitions in Fe II applied to HST spectra of chi Lupi
Authors: Nilsson, H.; Sikström, C. M.; Li, Z. S.; Lundberg, H.;
   Raassen, A. J. J.; Johansson, S.; Leckrone, D. S.; Svanberg, S.
Bibcode: 2000A&A...362..410N
Altcode:
  Radiative lifetimes for six highly excited levels in Fe II have been
  measured at Lund Laser Centre applying the laser induced fluorescence
  technique and two-step excitation. The energy levels belong to the
  even-parity 3d<SUP>6</SUP>(<SUP>5</SUP>D)4d subconfiguration at about
  10 eV. Branching fractions (BF:s) of 29 transitions from these levels
  to the 3d<SUP>6</SUP>(<SUP>5</SUP>D)4p subconfiguration at about 5
  eV have been measured in the wavelength region 2000-3000 Å with the
  Lund Fourier Transform Spectrometer. By normalizing the BF:s with the
  lifetimes we get experimental oscillator strengths for these 29 4p-4d
  lines. The oscillator strengths are compared with new theoretical
  calculations using the orthogonal operator technique and applied to
  high-resolution spectra of the star chi Lupi, recorded with the Hubble
  Space Telescope.

Title: New forbidden and fluorescent Fe III lines identified in HST
    spectra of eta Carinae
Authors: Johansson, S.; Zethson, T.; Hartman, H.; Ekberg, J. O.;
   Ishibashi, K.; Davidson, K.; Gull, T.
Bibcode: 2000A&A...361..977J
Altcode:
  We discuss the origin of eight emission lines in the spectra of
  gas blobs close to the central star of eta Carinae. The spectra
  have been obtained with the Goddard High Resolution Spectrograph
  (GHRS) and the Space Telescope Imaging Spectrograph (STIS) onboard
  the Hubble Space Telescope. Between 2400 and 2500 Å five narrow
  lines are identified as new forbidden lines of doubly ionized iron,
  [Fe III]. We present gA-value data for the corresponding transitions,
  which combine two different metastable configurations of Fe III. An
  anomalous intensity of the narrow Fe III line (UV 34) at 1914 Å is
  explained as fluorescence due to HLyalpha pumping. A level mixing of
  about 1% increases the f-value of the pumped excitation channel by
  more than two orders of magnitude, which makes the pumping efficient
  and the fluorescence significant. We introduce a new designation for
  fluorescence lines photoexcited by an accidental resonance, eg. &lt; Fe
  III&gt; in the case of doubly ionized iron. Based on observations with
  the NASA/ESA Hubble Space Telescope, and supported by grant numbers
  GO-6501 and GO-7302 from the Space Telescope Science Institute. The
  STScI is operated by the Association of Universities for Research in
  Astronomy, Inc., under NASA contract NAS5-26555.

Title: Ultraviolet fluorescence lines of Fe II observed in satellite
    spectra of the symbiotic star RR Telescopii
Authors: Hartman, H.; Johansson, S.
Bibcode: 2000A&A...359..627H
Altcode:
  By examining all emission lines of Fe II in high resolution satellite
  spectra of the symbiotic star RR Tel we have made a systematic study
  of fluorescence lines in the ultraviolet wavelength region 1200-3000
  Ä. We list 33 energy levels of Fe II that are selectively excited
  in the stellar system by photons from strong lines of H, He II, Si
  III, O III, C IV, O V, Ne V, and O VI. All energy levels listed are
  accompanied by the most probable pumping line. The subsequent decay
  from the pumped levels results in about 120 fluorescence lines observed
  in spectra recorded with the International Ultraviolet Explorer and
  the Hubble Space Telescope. The tables include 9 energy levels and 17
  emission lines of Fe II, which are for the first time attributed to
  fluorescence. In a finding list we also include potential fluorescence
  lines, which means additional transitions from the pumped energy levels
  observed in laboratory spectra but not in the stellar spectra. Based on
  observations by the International Ultraviolet Explorer (IUE) and the
  Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space
  Telescope (HST). Tables 1-5 are only available electronically with
  the On-Line publication at http://link.springer.de/link/service/00230/

Title: [Sr II] Detected in a Nebular Filament Near Eta Carinae
Authors: Gull, T.; Zethson, T.; Hartman, H.; Johansson, S.; Davidson,
   K.; Ishibashi, K.
Bibcode: 2000AAS...196.0508G
Altcode: 2000BAAS...32..682G
  Observations with the Space Telescope Imaging Spectrograph on the Hubble
  Space Telescope reveal a peculiar emission line region in the close
  vicinity to Eta Carinae. The lines of [SrII], [MnII], [CoII], [TiII],
  [NiII] and [FeI] are detected in the 6400-7000A spectral interval at
  a blue-shifted velocity of 95 km/sec and seem to be associated with a
  long, narrow filament with dimensions of &lt;0.5" by 1.1". The filament
  is notable as it is separate both in velocity and structure from the
  bright emission of the Integral Nebula. This filament is buried within
  the Homunculus and is not visible in direct images which are dominated
  by reflection nebulosities. In our literature searches we have found
  no evidence of strontium emission lines in nebulae. We are aware of
  permitted transitions of strontium seen in AGB stars. S-processed
  elements like strontium are not expected in the ejecta of a massive
  star like Eta Carinae. Detection of [SrII] and the fact that the [NiII],
  [MnII] and [CoII] lines are unusually strong compared to [FeI] are quite
  a surprise. It has long been known that nitrogen is overabundant in
  the ejecta of Eta Carinae. Is this processed material from the present
  star(s)? Has there been processed material ejected from a more evolved
  companion? The situation is decidedly mysterious. This research has
  been supported by NASA through STScI grants and the STIS GTO funding.

Title: The FERRUM Project
Authors: Johansson, S.; Lundberg, H.; Li, Z.; Nilsson, H.; Sikström,
   C. M.; Zethson, T.; Hartman, H.; Karlsson, H.; Dolk, L.; Mannervik,
   S.; Raassen, T.; Leckrone, D.
Bibcode: 2000IAUJD...1E..20J
Altcode:
  The FERRUM project aims at improving the database for oscillator
  strengths in iron group elements with an emphasis on astrophysically
  important ions. The international collaboration includes experts on
  experimental, theoretical and observational data. The first results
  concern Fe II. Experimental radiative lifetimes (LIF technique) for
  some particular levels of Fe II are combined with experimental (FT
  spectroscopy) and theoretical branching fractions to obtain absolute
  oscillator strengths, which are then compared with new theoretical
  data (orthogonal operator technique). Depending on the agreement
  complementary theoretical data are included. The new data are tested
  in stellar spectra (HST, NOT). We have obtained f-values for Fe II
  lines in the UV and optical regions originating from lower levels
  with excitation energies in the range 3-10 eV. The lines belong to
  four different transition arrays. The difference between experimental
  and theoretical data is of the order of 10%. The new data provide
  independent and new lines for abundance analysis and a test of LTE
  conditions in stellar atmospheres. Lifetimes of metastable states are
  measured at a storage ring, providing the first experimental data for
  forbidden lines, [Fe II].

Title: Commission 14: Atomic and Molecular Data: (Donnees Atomiques
    et Moleculaires)
Authors: Rostas, F.; Smith, P. L.; Berrington, K. A.; Feautrier, N.;
   Grevesse, N.; Johansson, S.; Jørgensen, U. G.; Martin, W. C.; Mason,
   H.; Parkinson, W.; Tchang-Brillet, W. -Ü. L.
Bibcode: 2000IAUTA..24..380R
Altcode:
  No abstract at ADS

Title: New Zr II oscillator strengths and the zirconium conflict in
    the HgMn star chi LUPI
Authors: Sikström, C. M.; Lundberg, H.; Wahlgren, G. M.; Li, Z. S.;
   Lynga, C.; Johansson, S.; Leckrone, D. S.
Bibcode: 1999A&A...343..297S
Altcode:
  Lifetimes on the sub-nanosecond scale for the levels v(2) D_{3/2}, v(2)
  F_{3/2} and v(2) F_{5/2} in the 4d5s5p configuration in Zr II have been
  measured, using the method of laser-induced fluorescence. Combined with
  branching fractions obtained with the Lund Ultraviolet (UV) Fourier
  Transform Spectrometer (FTS), experimental oscillator strengths have
  been derived. From Hubble Space Telescope/Goddard High-Resolution
  Spectrograph spectra, the zirconium abundance in the HgMn star chi
  Lupi has been determined from Zr II and Zr III lines. More than an
  order of magnitude difference in the Zr II abundance has been derived
  from these ionization stages. The difference is much too large to
  be explained by uncertainties in the oscillator strengths. Possible
  explanations of this difference have to be found in the stellar models,
  such as the influence of non-LTE or diffusion.

Title: Strange Velocities in the Equatorial Ejecta of η Carinae
Authors: Zethson, T.; Johansson, S.; Davidson, K.; Humphreys, R. M.;
   Ishibashi, K.; Ebbets, D.
Bibcode: 1999ASPC..179..123Z
Altcode: 1999ecm..conf..123Z
  No abstract at ADS

Title: Atomic Physics Aspects on Previously and Newly Identified
    Iron Lines in the HST Spectrum of η Carinae
Authors: Johansson, S.; Zethson, T.
Bibcode: 1999ASPC..179..171J
Altcode: 1999ecm..conf..171J
  No abstract at ADS

Title: Emission line profiles in the spectrum of υ Sgr (poster)
Authors: Strid, K.; Kalus, G.; Johansson, S.; Wahlgren, G. M.;
   Zapadlik, I.; Ardeberg, A.; Lundström, I.
Bibcode: 1999anot.conf..252S
Altcode:
  No abstract at ADS

Title: The Spectrum and Term Analysis of Co II
Authors: Pickering, Juliet C.; Raassen, A. J. J.; Uylings, P. H. M.;
   Johansson, S.
Bibcode: 1998ApJS..117..261P
Altcode:
  High-resolution spectra of singly ionized cobalt have been recorded by
  Fourier transform spectrometry in the region 1420-33333 Å (70422-3000
  cm<SUP>-1</SUP>) with cobalt-neon and cobalt-argon hollow cathode
  lamps as sources. Most of the Co II lines exhibit broadening due to
  hyperfine structure, but the wavenumber uncertainty for the center of
  gravity of the strongest lines is less than 0.002 cm<SUP>-1</SUP>. Of
  the previously listed energy levels of Co II, 215 have been revised
  and six have been discarded. In addition, 171 new levels have been
  found of which 125 are reported here for the first time. The number of
  classified lines has doubled with wavenumbers and classifications being
  presented for 2373 Co II lines, of which 1242 involve the new levels.

Title: The Impact of GHRS on Atomic Physics - A Fruitful Collaboration
    Between Laboratory and Stellar Spectroscopy
Authors: Johansson, S.; Leckrone, D. S.; Davidson, K.
Bibcode: 1998ASPC..143..155J
Altcode: 1998sigh.conf..155J
  No abstract at ADS

Title: Abundances and Isotopic Compositions of Singly Ionized Platinum
    in Chi LUPI and HR 7775
Authors: Kalus, G.; Johansson, S.; Wahlgren, G. M.; Leckrone, D. S.;
   Brandt, J. C.; Thorne, A. P.
Bibcode: 1998ASPC..143..326K
Altcode: 1998sigh.conf..326K
  No abstract at ADS

Title: High-Resolution Observation of B II A1362 in Chi LUPI
Authors: Zethson, T.; Johansson, S.; Wahlgren, G. M.; Leckrone, D. S.
Bibcode: 1998ASPC..143..339Z
Altcode: 1998sigh.conf..339Z
  No abstract at ADS

Title: Atomic Calculations Inspired by the GHRS - gf-Values, Hyperfine
    Structure Constants, and Isotope Shifts for Heavy Elements
Authors: Brage, T.; Proffitt, C. R.; Wahlgren, G. M.; Leckrone, D. S.;
   Johansson, S.
Bibcode: 1998ASPC..143..378B
Altcode: 1998sigh.conf..378B
  No abstract at ADS

Title: Very Heavy Elements in the HgMn Star Chi LUPI
Authors: Wahlgren, G. M.; Leckrone, D. S.; Brage, T.; Proffitt, C. R.;
   Johansson, S.
Bibcode: 1998ASPC..143..330W
Altcode: 1998sigh.conf..330W
  No abstract at ADS

Title: The Abundance of CO in the HgMn Star Chi LUPI
Authors: Zethson, T.; Johansson, S.; Wahlgren, C. M.; Pickering, J.;
   Leckrone, D. S.
Bibcode: 1998ASPC..143..334Z
Altcode: 1998sigh.conf..334Z
  No abstract at ADS

Title: Oscillator Strengths and the Rhodium Abundance in the HgMn
    Type Star Chi LUPI
Authors: Lundberg, H.; Johansson, S.; Litzen, U.; Wahlgren, C. M.;
   Leckrone, D. S.
Bibcode: 1998ASPC..143..343L
Altcode: 1998sigh.conf..343L
  No abstract at ADS

Title: Strange velocities in the equatorial ejecta of Eta Carinae
Authors: Davidson, K.; Zethson, T.; Johansson, S.; Ishibashi, K.;
   Ebbets, D.
Bibcode: 1997AAS...191.3406D
Altcode: 1997BAAS...29R1261D
  In 1996--1997 we obtained HST/GHRS and HST/FOS data on locations thought
  be be in the equatorial ejecta of Eta Carinae. One motivation was a
  desire to test the age of the equatorial debris-disk, which, according
  to some evidence, may be younger than the bipolar lobes. In fact,
  however, the velocities are inconsistent with both of the obvious
  models. The observed values may indicate the presence of old, slow
  material, or that the geometrical situation has been misinterpreted,
  or something else even more bizarre. This is one more instance
  of an important detail concerning Eta Car that should have been
  straightforward but which turns out instead to be, essentially,
  not understood.

Title: The Boron Isotope Ratio in HD 76932
Authors: Rebull, L.; Duncan, D.; Johansson, S.; Thorburn, J.; Fields,
   B.; Schramm, D.
Bibcode: 1997AAS...191.1305R
Altcode: 1997BAAS...29.1230R
  Data in the lambda 2090 B region of HD 76932 were obtained using the
  HST GHRS echelle at a resolution of 90,000. This wavelength region has
  been previously identified as a likely candidate for observing the (11)
  B/(10) B isotopic splitting (Johansson et al. 1993). Data presented
  here provides some constraints on the isotopic ratio, but it is not
  certain whether or not the line in question is blended with unknown
  stellar absorption feature(s), making an unambiguous detection of the
  isotopic ratio impossible. The constraints that can be placed on the
  isotopic ratio based on these data are discussed.

Title: Status of the AMANDA and BAIKAL Neutrino Telescopes
Authors: Askebjer, P.; Barwick, S. W.; Bay, R.; Bergström, L.;
   Bouchta, A.; Carius, S.; Dahlberg, E.; Engel, K.; Erlandsson, B.;
   Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth,
   P. O.; Hundertmark, S.; Jacobsen, J.; Johansson, S.; Kandhadai, V.;
   Karle, A.; Liubarsky, I.; Lowder, D.; Mikolajski, T.; Miller, T. C.;
   Mock, P.; Morse, R.; Nygren, D.; Porrata, R.; Price, P. B.; Richards,
   A.; Rubinstein, H.; Schneider, E.; Spiering, C.; Streicher, O.; Sun,
   Q.; Thon, T.; Tilav, S.; Walck, C.; Wiebusch, C.; Wischnewski, R.;
   Yodh, G.; Belolaptikov, I. A.; Bezrukov, L. B.; Borisovets, B. A.;
   Budnev, N. M.; Chensky, A. G.; Danilchenko, I. A.; Djilkibaev,
   Zh. -A. M.; Dobrynin, V. I.; Domogatsky, G. V.; Doroshenko,
   A. A.; Fialkovsky, S. V.; Gaponenko, O. N.; Garus, A. A.; Gress,
   T. A.; Ignat'ev, S. B.; Karle, A.; Klabukov, A. M.; Klimov, A. I.;
   Klimushin, S. I.; Koshechkin, A. P.; Kulepov, V. F.; Kuzmichev, L. A.;
   Lubsandorzhiev, B. K.; Mikolajski, T.; Milenin, M. B.; Mirgazov,
   R. R.; Moroz, A. V.; Moseiko, N. I.; Nikiforov, S. A.; Osipova,
   E. A.; Pandel, D.; Panfilov, A. I.; Parfenov, Yu. V.; Pavlov, A. A.;
   Petukhov, D. P.; Pocheikin, K. A.; Pokhil, P. G.; Pokolev, P. A.;
   Rosanov, M. I.; Rubzov, V. Yu.; Sinegovsky, S. I.; Sokalski, I. A.;
   Spiering, Ch.; Streicher, O.; Tarashansky, B. A.; Thon, T.; Wiebusch,
   C.; Wischnewski, R.
Bibcode: 1997NuPhS..52..256A
Altcode:
  No abstract at ADS

Title: Defining the chi LUPI Abundance Peak Among the 5d and 6p
    Elements
Authors: Wahlgren, G. M.; Leckrone, D. S.; Brage, T.; Johansson, S.;
   Proffitt, C. R.
Bibcode: 1996AAS...189.7811W
Altcode: 1996BAAS...28.1378W
  Using the echelle mode of the Hubble Space Telescope/Goddard High
  Resolution Spectrograph, observations of the extremely sharp-lined HgMn
  star chi Lupi have provided new insights into the ultraviolet spectrum,
  both for the purposes of astrophysics and atomic spectroscopy. Testing
  the diffusion paradigm, generally believed to be the dominant influence
  in creating the plethora of spectral line strength anomalies in HgMn
  stars, requires knowledge of the isotope mixture at several ionization
  stages. Our exciting data for the element mercury provided the impetus
  to expand our study to include other heavy elements. The high quality
  GHRS spectra have placed stringent requirements upon the accuracy of the
  atomic data utilized in our synthetic spectrum analyses. Therefore,
  we have undertaken a concerted effort to employ both laboratory
  techniques and theoretical calculations in order to provide such
  needed data. As a result of this effort we are now able to nearly
  fully define quantitatively the abundance distribution in this star
  over the element range defined by the 5d elements tungsten (Z = 74)
  through mercury (Z = 80) and the 6p elements thallium (Z = 81) through
  bismuth (Z = 83). We present new abundance determinations for several
  of these elements, the result of which is to emphasize the presence of
  a peak in the abundance distribution, defined by the elements platinum
  (Z = 78) through thallium (Z = 81). This peak, with abundances four
  to five orders of magnitude greater than the solar system values, is
  present for the three lowest stages of ionization and is broader than
  either the r- or s-process peaks that are found in this vicinity of
  the periodic table in the solar system elemental abundance distribution.

Title: Branching Fractions and Oscillator Strengths for Fe II
    Transitions from the 3d 6( 5D)4p Subconfiguration
Authors: Bergeson, S. D.; Mullman, K. L.; Wickliffe, W. E.; Lawler,
   J. E.; Litzen, U.; Johansson, S.
Bibcode: 1996ApJ...464.1044B
Altcode:
  New experimental branching fractions and transition probabilities
  are reported for 56 transitions in Fe II. The branching fractions
  are measured with a Fourier transform spectrometer and also with a
  high-resolution grating spectrometer on an optically thin hollow cathode
  discharge. Highly accurate experimental radiative lifetimes from the
  recent literature provide the normalization required to convert our
  branching fractions into absolute transition probabilities. Results are
  compared with experimental and theoretical values in the literature. Our
  new transition probabilities will establish the absolute scale for
  relative absorption oscillator strengths of vacuum ultraviolet lines
  measured using a new high-sensitivity absorption experiment at the
  University of Wisconsin.

Title: Is there a Dichromatic UV Laser in Eta Carinae?
Authors: Johansson, S.; Davidson, K.; Ebbets, D.; Weigelt, G.; Balick,
   B.; Frank, A.; Hamann, F.; Humphreys, R. M.; Morse, J.; White, R. L.
Bibcode: 1996swhs.conf..361J
Altcode:
  No abstract at ADS

Title: Investigating fluorescence mechanisms in the atmosphere of
    the cool, supergiant star alpha ORI
Authors: Wahlgren, G. M.; Johansson, S.
Bibcode: 1996ASPC..109..551W
Altcode: 1996csss....9..551W
  No abstract at ADS

Title: Term analysis of a complex spectrum.
Authors: Johansson, S.
Bibcode: 1996PhST...65....7J
Altcode:
  A term analysis of a complex spectrum is like a giant jigsaw puzzle
  with pieces of different sizes, shapes, colours, etc., and the result
  is a picture of the atomic structure of an atom or ion having several
  valence electrons. This knowledge of the atomic structure tests the
  theoretical model of complex atoms and theoretical calculations of
  various atomic parameters. These atomic parameters are fundamental
  ingredients in, e.g. abundance analyses of astrophysical spectra. The
  author discusses the atomic structure of transition group elements
  based on term analyses of their spectra. He gives examples from Fe II
  and Zr II. The strong coupling to high-resolution stellar spectroscopy,
  in particular in the satellite ultraviolet and near-infrared wavelength
  regions, is emphasized. Missing atomic data for transition elements
  is still the main reason for missing opacity in stellar spectra,
  calculated from stellar model atmospheres.

Title: Atomic Data for High Resolution Stellar Spectroscopy: A Review
Authors: Johansson, S.; Leckrone, D. S.
Bibcode: 1996ASPC..108..113J
Altcode: 1996mass.conf..113J
  No abstract at ADS

Title: Stellar chemical abundances with the GHRS.
Authors: Leckrone, D. S.; Johansson, S.; Wahlgren, G. M.; Proffitt,
   C. R.; Brage, T.
Bibcode: 1996PhST...65..110L
Altcode:
  The accurate quantitative analysis of high resolution ultraviolet
  spectra of ultra-sharp-lined, early-type, chemically peculiar
  stars, obtained with the Goddard High Resolution Spectrograph on
  the Hubble Space Telescope, has been made possible by the synergism
  between state-of-the-art astrophysics and state-of-the-art atomic
  spectroscopy. The authors illustrate this with several examples,
  including the discovery of spin-forbidden "parasite" transitions of Fe
  II, the first observations of hyperfine components and isotopic shifts
  of stellar lines of thallium, and measurements of the photospheric
  abundances of a large number of normally trace elements.

Title: High excitation Rydberg levels of Fe I from the ATMOS solar
    spectrum at 2.5 and 7 μm.
Authors: Schoenfeld, W. G.; Chang, E. S.; Geller, M.; Johansson, S.;
   Nave, G.; Sauval, A. J.; Grevesse, N.
Bibcode: 1995A&A...301..593S
Altcode:
  The quadrupole-polarization theory has been applied to the
  3d^6^4s(^6^D)4f and 5g subconfigurations of Fe I by a parametric fit,
  and the fitted parameters are used to predict levels in the 6g and
  6h subconfigurations. Using the predicted values, we have computed
  the 4f-6g and 5g-6h transition arrays and made identifications in the
  ATMOS infrared solar spectrum. The newly identified 6g and 6h levels,
  based on ATMOS wavenumbers, are combined with the 5g levels and found to
  agree with the theoretical values with a root mean-squared-deviation of
  0.042cm^-1^. Our approach yields a polarizability of 28.07 a_o_^3^and
  a quadrupole moment of 0.4360+/-0.0010ea_o_^2^for Fe II, as well as
  an improved ionization potential of 63737.700+/-0.010cm^-1^ for Fe I.

Title: Fluorescence lines of MnII in the red spectrum of η Carinae.
Authors: Johansson, S.; Wallerstein, G.; Gilroy, K. K.; Joueizadeh, A.
Bibcode: 1995A&A...300..521J
Altcode:
  Five emission lines in the wavelength region 6122-6132 A in the
  spectrum of η Carinae are identified as the 4d ^5^D-4f ^5^F multiplet
  of Mn^44^Sc II. These are the only high-excitation lines of Mn^44^Sc
  II present in the spectrum. The upper levels of the multiplet are most
  likely populated through photoexcitation by an accidental coincidence
  in wavelength between the ultraviolet multiplets UV 15 of Mn^44^Sc
  II and UV 5 of Si^44^Sc II. Improved laboratory wavelengths for the
  Mn^44^Sc II lines are presented.

Title: Initial Analysis of Coincident Events Between the SPASE and
    AMANDA Detectors
Authors: Miller, T.; Beaman, J.; Evenson, P. A.; Gaisser, T. K.; Hart,
   S.; Lloyd-Evans, J.; Martello, D.; Ogden, P.; Petrakis, J.; Stanev,
   Todor; Watson, A. A.; Askebjer, P.; Barwick, S. W.; Bergström,
   L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.;
   Hallgren, L. A.; Halzen, F.; Hulth, P. O.; Jacobsen, J.; Johansson,
   S.; Kandhadai, V.; Liubarsky, I.; Lowder, D. M.; Miller, T.; Mock,
   P.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein,
   H.; Sun, Q.; Tilav, S.; Walck, C.; Yodh, G.
Bibcode: 1995NuPhS..43..245M
Altcode:
  We report on the status of the SPASE-AMANDA coincidence experiment.

Title: VizieR Online Data Catalog: New multiplet table for FeI
    (Nave+, 1994)
Authors: Nave, G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.;
   Brault, J. W.
Bibcode: 1995yCat..20940221N
Altcode:
  We have recorded spectra of iron-neon and iron-argon hollow cathode
  lamps in the region 1700A-5um (59,000-2000cm<SUP>-1</SUP>), with Fourier
  transform (FT) spectrometers at the National Solar Observatory, Tucson,
  Arizona, and Imperial College, London, UK, and with a high-resolution
  grating spectrograph at the National Institute of Standards and
  Technology, Gaithersburg, Maryland. The uncertainty of the strongest
  lines in the FT spectra is less than 0.002cm<SUP>-1</SUP> (0.2mA at
  3000A; 8mA at 2um). Pressure- and current-dependent shifts are less
  than 0.001cm<SUP>-1</SUP> for transitions between low-lying levels,
  increasing to 0.006cm<SUP>-1</SUP> for transitions between the most
  highly excited levels. We report 28 new energy levels of Fe I and
  revised values of another 818 levels. We have identified 9501 lines as
  due to 9759 transitions in Fe I, and these are presented in the form
  of a new multiplet table and finding list. This compares with the ~5500
  lines due to 467 energy levels in the multiplet tables of Moore (1950,
  NBS Circ., No.488 and 1959, NBS Tech. note 30). The biggest increase is
  in the near-ultraviolet and near infrared, and many of the new lines
  are present in the solar spectrum. Experimental log (gf) values are
  included where they are available. A further 125 unidentified lines
  due to Fe I are given. (4 data files).

Title: Optical Properties of the South Pole Ice at Depths Between
    0.8 and 1 Kilometer
Authors: Askebjer, P.; Barwick, S. W.; Bergstrom, L.; Bouchta, A.;
   Carius, S.; Coulthard, A.; Engel, K.; Erlandsson, B.; Goobar, A.; Gray,
   L.; Hallgren, A.; Halzen, F.; Hulth, P. O.; Jacobsen, J.; Johansson,
   S.; Kandhadai, V.; Liubarsky, I.; Lowder, D.; Miller, T.; Mock, P. C.;
   Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H.;
   Schneider, E.; Sun, Q.; Tilav, S.; Walck, C.; Yodh, G.
Bibcode: 1995Sci...267.1147A
Altcode:
  The optical properties of the ice at the geographical South Pole
  have been investigated at depths between 0.8 and 1 kilometer. The
  absorption and scattering lengths of visible light (~515 nanometers)
  have been measured in situ with the use of the laser calibration setup
  of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino
  detector. The ice is intrinsically extremely transparent. The measured
  absorption length is 59 ± 3 meters, comparable with the quality
  of the ultrapure water used in the Irvine-Michigan-Brookhaven and
  Kamiokande proton-decay and neutrino experiments and more than twice
  as long as the best value reported for laboratory ice. Because of a
  residual density of air bubbles at these depths, the trajectories of
  photons in the medium are randomized. If the bubbles are assumed to
  be smooth and spherical, the average distance between collisions at
  a depth of 1 kilometer is about 25 centimeters. The measured inverse
  scattering length on bubbles decreases linearly with increasing depth
  in the volume of ice investigated.

Title: Measurements of the Absorption Length of the Ice at the South
    Pole in the Wavelength Interval 410 nm to 610 nm
Authors: Erlandsson, B.; Askebjer, P.; Barwick, S. W.; Bergström,
   L.; Bouchta, A.; Carius, S.; Goobar, A.; Gray, L.; Hallgren, A.;
   Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson,
   S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D.; Miller,
   T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards,
   A.; Rubinstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Tilav, S.; Walck,
   C.; Wishnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1.1039E
Altcode: 1995ICRC...24a1039E
  No abstract at ADS

Title: Status and Capabilities of AMANDA-94
Authors: Mock, P. C.; Askebjer, P.; Barwick, S. W.; Bergström,
   L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.;
   Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.;
   Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D.;
   Miller, T. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.;
   Rubenstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Tilav, S.; Walck,
   C.; Wischnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1..758M
Altcode: 1995ICRC...24a.758M
  No abstract at ADS

Title: Analysis of High-Resolution Laboratory Spectra of Iron and
    Identification of Fe I Lines in the Solar Spectrum
Authors: Nave, G.; Johansson, S.
Bibcode: 1995ASPC...81..197N
Altcode: 1995lahr.conf..197N
  No abstract at ADS

Title: SPASE -- AMANDA Coincidences At The South Pole
Authors: Miller, T. C.; Gaisser, T. K.; Hart, S.; Lloyd-Evans, J.;
   Martello, D.; Petrakis, J.; Stanev, T.; Watson, A. A.; Askebjer, P.;
   Barwick, S. W.; Bergstrom, L.; Bouchta, A.; Carius, S.; Erlandsson,
   B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.;
   Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.;
   Liubarksky, I.; Lowder, D.; Miller, T. C.; Mock, P.; Porrata, R.;
   Price, P. B.; Richards, A.; Rubinstein, H; Schneider, E.; Spiering,
   C.; Sun, Q.; Tilav, S.; Walck, C.; Wischnewski, R.; Yodh, G.
Bibcode: 1995ICRC....2..768M
Altcode: 1995ICRC...24b.768M
  No abstract at ADS

Title: Indirect Evidence for Long Absorption Lengths in Antarctic Ice
Authors: Tilav, S.; Askebjer, P.; Barwick, S. W.; Bergström, L.;
   Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.;
   Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen,
   J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder,
   D. M.; Martello, D.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata,
   R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun,
   Q.; Thon, T.; Walck, C.; Wishnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1.1011T
Altcode: 1995ICRC...24a1011T
  No abstract at ADS

Title: Isotope Shift in Pt II Observed in Laboratory FTS Spectra
Authors: Kalus, G. M.; Johansson, S.; Thorne, A. P.; Leckrone, D. S.;
   Wahlgren, G. M.
Bibcode: 1995ASPC...81..239K
Altcode: 1995lahr.conf..239K
  No abstract at ADS

Title: Improved Wavelengths and Extended Analysis of TI II
Authors: Zapadlik, I.; Johansson, S.; Litzen, U.
Bibcode: 1995ASPC...81..237Z
Altcode: 1995lahr.conf..237Z
  No abstract at ADS

Title: The Design of a Neutrino Telescope Using Natural Deep Ice as
    a Particle Detector
Authors: Gray, L.; Askebjer, P.; Barwick, S. W.; Bergström, L.;
   Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Hallgren, A.;
   Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson,
   S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D. M.; Miller,
   T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards,
   A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Tilav, S.; Thon, T.; Walck,
   C.; Wishnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1..816G
Altcode: 1995ICRC...24a.816G
  No abstract at ADS

Title: Optical Properties of South Pole Ice for Neutrino Astrophysics
Authors: Price, P. B.; Askebjer, P.; Barwick, S. W.; Bergstrom,
   L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.;
   Hallgreen, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen,
   J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder,
   D. M.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Richards,
   A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Tilav, S.; Walck, C.;
   Westphal, A. J.; Wischnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1..777P
Altcode: 1995ICRC...24a.777P
  No abstract at ADS

Title: Remote Surveys of AMANDA
Authors: Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.;
   Carius, S.; Engel, K.; Erlandsson, B.; Gaisser, T. K.; Goobar, A.;
   Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.;
   Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.;
   Lowder, D. M.; Martello, D.; Miller, T. C.; Mock, P. C.; Morse, R.;
   Porrata, R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering,
   C.; Sun, Q.; Thon, T.; Tilav, S.; Walck, C.; Wishnewski, R.; Yodh, G.
Bibcode: 1995ICRC....1.1009A
Altcode: 1995ICRC...24a1009A
  No abstract at ADS

Title: High Resolution Spectroscopy of Singly Ionized Transition
    Elements
Authors: Johansson, S.
Bibcode: 1995ASPC...81..151J
Altcode: 1995lahr.conf..151J
  No abstract at ADS

Title: A New Multiplet Table for Fe i
Authors: Nave, G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.;
   Brault, J. W.
Bibcode: 1994ApJS...94..221N
Altcode:
  We have recorded spectra of iron-neon and iron-argon hollow cathode
  lamps in the region 1700 A-5 micrometers (59,000-2000/cm), with Fourier
  transform (FT) spectrometers at the National Solar Observatory, Tucson,
  Arizona, and Imperial College, London, UK, and with a high-resolution
  grating spectrograph at the National Institute of Standards and
  Technology, Gaithersburg, Maryland. The uncertainty of the strongest
  lines in the FT spectra is less than 0.002/cm (0.2 mA at 3000 A; 8 mA
  at 2 micrometers). Pressure- and current-dependent shifts are less
  than 0.001/cm for transitions between low-lying levels, increasing
  to 0.006 cm<SUP>-1</SUP> for transitions between the most highly
  excited levels. We report 28 new energy levels of Fe I and revised
  values of another 818 levels. We have identified 9501 lines as due to
  9759 transitions in Fe I, and these are presented in the form of a new
  multiplet table and finding list. This compares with the approximately
  5500 lines due to 467 energy levels in the multiplet tables of Moore
  (1950, 1959). The biggest increase is in the near-ultraviolet and
  near infrared, and many of the new lines are present in the solar
  spectrum. Experimental log (gf) values are included where they are
  available. A further 125 unidentified lines due to Fe I are given. The
  tables are also available in computer-readable form.

Title: UV-spektra från Hubble-teleskopet avslöjar en stjärna i
    Vargen som lagrar tunga isotoper av mycket tunga grundämnen.
Authors: Johansson, S. E.; Leckrone, D. S.; Wahlgren, G. M.
Bibcode: 1994ATi....27..113J
Altcode:
  UV spectra from the Hubble Space Telescope reveal a star that stores
  heavy isotopes of very heavy elements. Atomic and plasma physics
  arguments for UV spectroscopy from space borne observatories are
  given. As an example, the authors discuss the analysis of high
  resolution spectra of the chemically peculiar star χ Lupi, obtained
  with the Hubble Space Telescope, in terms of identification of spectral
  lines of very heavy elements.

Title: Analysis of the 3d 64 s( 6D)4f--5g Supermultiplet of Fe i in
    Laboratory and Solar Infrared Spectra
Authors: Johansson, S.; Nave, G.; Geller, M.; Sauval, A. J.; Grevesse,
   N.; Schoenfeld, W. G.; Change, E. S.; Farmer, C. B.
Bibcode: 1994ApJ...429..419J
Altcode: 1994astro.ph..4050J
  The combined laboratory and solar analysis of the highly-excited
  subconfigurations 4f and 5g of Fe I has allowed us to classify 87
  lines of the 4f-5g supermultiplet in the spectral region 2545-2585
  cm-1. The level structure of these JK-coupled configurations
  is predicted by semiempirical calculations and the quadrupolic
  approximation. Semiempirical gf-values have been calculated and
  are compared to gf values derived from the solar spectrum. The solar
  analysis has shown that these lines, which should be much less sensitive
  than lower excitation lines to departures from LTE and to temperature
  uncertainties, lead to a solar abundance of iron which is consistent
  with the meteoritic value (A_Fe = 7.51).

Title: A glimpse into the post-COSTAR GHRS: detections of As II and
    Bi II in the UV spectrum of the HgMn star χ Lupi.
Authors: Wahlgren, G. M.; Brage, T.; Gilliland, R. L.; Johansson,
   S.; Leckrone, D. S.; Lindler, D. J.
Bibcode: 1994BAAS...26..869W
Altcode:
  No abstract at ADS

Title: A New Multiplet Table for Fe
Authors: Nave, I. G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.;
   Brault, J. W.
Bibcode: 1994astro.ph..4049N
Altcode:
  We have recorded spectra of iron-neon and iron-argon hollow cathode
  lamps in the region 1700A -- 5um (59000 -- 2000cm-1), with Fourier
  transform (FT) spectrometers at the National Solar Observatory,
  Tucson, Arizona, U.S.A. and Imperial College, London, U.K., and with
  a high resolution grating spectrograph at the National Institute of
  Standards and Technology, Gaithersburg, U.S.A. The uncertainty of the
  strongest lines in the FT spectra is &lt;0.002cm-1 (0.2mA at 3000A;
  8mA at 2um). Pressure and current-dependent shifts are &lt;0.001cm-1
  for transitions between low lying levels, increasing to 0.006 cm-1 for
  transitions between the most highly excited levels. We report 28 new
  energy levels of Fe I and revised values of another 818 levels. We
  have identified 9501 lines as due to 9759 transitions in Fe I, and
  these are presented in the form of a new multiplet table and finding
  list. This compares with the 5500 lines due to 467 energy levels in
  the multiplet tables of Moore (1950, 1959). The biggest increase is in
  the near ultraviolet and near infra-red, and many of the new lines are
  present in the solar spectrum. Experimental log(gf) values are included
  where available. A further 125 unidentified lines due to Fe I are given.

Title: Analysis of Very High Excitation Fe I Lines (4f - 5g) in the
    Solar Infrared Spectrum
Authors: Johansson, S.; Nave, G.; Geller, M.; Sauval, A. J.;
   Grevesse, N.
Bibcode: 1994IAUS..154..543J
Altcode:
  No abstract at ADS

Title: Highly-excited levels of Fe I obtained from laboratory and
    solar Fourier transform and grating spectra. II. Laboratory and
    solar identifications
Authors: Nave, G.; Johansson, S.
Bibcode: 1993A&AS..102..269N
Altcode:
  New identifications of ∼2200 Fe I lines between 1700 Å and 5 μm
  (59 000 cm<SUP>-1</SUP> -2000 cm<SUP>-1</SUP>) due to highly-excited
  configurations are presented. These have been observed in hollow cathode
  lamps using Fourier transform and grating spectroscopy. About 1700 of
  the lines have been observed in the solar spectrum. A companion paper
  presents the experimental energy levels.

Title: VizieR Online Data Catalog: Lab. and solar highly-excited
    levels of Fe I (Nave+ 1993)
Authors: Nave, G.; Johansson, S.
Bibcode: 1993yCat..41020269N
Altcode:
  New identifications of about 2200 FeI lines between 170nm and 5μm
  (59000 to 2000 cm<SUP>-1</SUP>) due to highly-excited configurations
  are presented. These have been observed in hollow cathode lamps using
  Fourier transform and grating spectroscopy. About 1700 if the lines
  have been observed in the solar spectrum. A companion paper presents
  the experimental energy levels. (1 data file).

Title: Highly-excited levels of Fe i obtained from laboratory and
    solar Fourier transform and grating spectra. 1. Energy levels
Authors: Nave, G.; Johansson, S.
Bibcode: 1993A&A...274..961N
Altcode:
  86 new levels due to the highly-excited configurations 3d64s(6D)nl,
  3d<SUP>6</SUP>4s(<SUP>6</SUP>D)nl, 3d<SUP>6</SUP>4s(<SUP>4</SUP>D)nl,
  and 3d<SUP>7</SUP>(<SUP>4</SUP>F)nl of Fe I have been established
  using visible and infra-red Fourier transform spectra of iron-neon and
  iron-argon hollow cathodes. 110 previously reported levels have also
  been revised to an accuracy of 0.003-0.005 cm<SUP>-1</SUP>. The levels
  were confirmed by comparison with ultraviolet spectra measured with a
  1O.7m grating spectrograph. A companion paper presents the identified
  lines in both laboratory and solar spectra.

Title: High resolution UV stellar spectroscopy with the HST/GHRS,
    challenges and opportunities for atomic physics.
Authors: Leckrone, D. S.; Johansson, S.; Wahlgren, G. M.; Adelman,
   S. J.
Bibcode: 1993PhST...47..149L
Altcode:
  The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space
  Telescope (HST) is producing ultraviolet spectra of unprecedented
  resolution and photometric quality. The authors illustrate this with
  observations of the ultra-sharp-lined, chemically peculiar B-type star,
  χ Lupi. The photosphere of this star is rich in heavy elements, and
  its UV spectrum is replete with transitions of species not commonly
  observed in astrophysical spectra. It is an excellent "laboratory"
  for atomic spectroscopy. Kurucz's comprehensive calculations of
  transition probabilities for the iron-group and other elements provides
  a reasonable starting point for theoretical spectrum synthesis. However,
  evidence is found of large systematic errors in his data base for
  transitions from particular energy levels in Fe II, Cr II, Co II,
  and other ions.

Title: Fluorescence lines in ultraviolet spectra of stars
Authors: Johansson, S.; Hamann, F. W.
Bibcode: 1993PhST...47..157J
Altcode:
  We discuss the presence of fluorescence lines that appear in stellar
  spectra in the satellite ultraviolet region between 1200 and 3200
  Å. Strong lines in partial multiplets result from a selective
  excitation, which in most cases is due to accidental wavelength
  coincidences. The prototype of photoexcitation by accidental resonance
  (PAR) is the classical Bowen mechanism. Photoexcitation by continuum
  radiation (PCR) is another source of selective population. <P />Besides
  a brief review of ultraviolet fluorescence lines identified in spectra
  of symbiotic stars and cool stars we discuss in detail two emission
  peaks at 2506-2508 Å. We give three different explanations for the
  appearance of this feature in IUE spectra of three different objects:
  RR Tel, η Car and KQ Pup. In connection to these lines we also
  discuss primary and secondary cascades in the near-infrared observed
  in high-resolution spectra. Comments are made on the strong Fe II line
  at 9997 Å.

Title: Using HST / GHRS Echelle Spectra as Templates for IUE Data
    Analysis
Authors: Wahlgren, G. M.; Leckrone, D. S.; Johansson, S.; Rosberg, M.
Bibcode: 1993ASPC...44..121W
Altcode: 1993pvnp.conf..121W; 1993IAUCo.138..121W
  No abstract at ADS

Title: Ly Alpha Pumping of Fe II in Quasars and AGN
Authors: Hamann, F.; Ferland, G.; Johansson, S.
Bibcode: 1992AAS...181.3512H
Altcode: 1992BAAS...24Q1174H
  No abstract at ADS

Title: Lyα pumping of Fe II in quasars and AGN.
Authors: Hamann, F.; Ferland, G.; Johansson, S.
Bibcode: 1992BAAS...24R1174H
Altcode:
  No abstract at ADS

Title: Fe II Emission from Qussars and AGN
Authors: Hamann, F.; Ferland, G.; Pradhan, A.; Johansson, S.
Bibcode: 1992AAS...179.6315H
Altcode: 1992BAAS...24R.682H
  No abstract at ADS

Title: Detection of high energy neutrinos in PAN
Authors: Bergström, L.; Johansson, S.
Bibcode: 1992hena.conf..309B
Altcode:
  No abstract at ADS

Title: Fe II emission from quasars and AGN.
Authors: Hamann, F.; Ferland, G.; Pradhan, A.; Johansson, S.
Bibcode: 1991BAAS...23R1424H
Altcode:
  No abstract at ADS

Title: Measuring the Energy of Multi-TeV Muons with a Water Cerenkov
    Detector
Authors: Johansson, S.
Bibcode: 1991ICRC....4..552J
Altcode: 1991ICRC...22d.552J
  No abstract at ADS

Title: New Identifications of Highly-Excited Fe I Lines Around 4μm
    in Cool Stars
Authors: Johansson, S.; Nave, G.; Learner, R. C. M.; Thorne, A. P.
Bibcode: 1991isrs.conf..189J
Altcode:
  No abstract at ADS

Title: High Resolution Atomic Spectroscopy in the Infrared and its
    Application to Astrophysics
Authors: Johansson, S.
Bibcode: 1991isrs.conf...87J
Altcode:
  No abstract at ADS

Title: New Identifications of Highly-Excited Fe I Lines Around 4
    μm in Cool Stars
Authors: Johansson, S.; Rosberg, M.; Hamann, F.
Bibcode: 1991isrs.conf..107J
Altcode:
  No abstract at ADS

Title: The Fe II Fluorescence Emission in UV Spectra of Symbiotics
    and Nuclei of Planetary Nebulae
Authors: Bruhweiler, F.; Feibelman, W. A.; Johansson, S.
Bibcode: 1990BAAS...22R1205B
Altcode:
  No abstract at ADS

Title: Gas dynamics, accretion and evolution of Algols: initial
    results for three representative systems
Authors: Gimenez, A.; Gonzalez-Riestra, R.; Guinan, E. F.; Kondo, Y.;
   McCluskey, G. E.; Bradstreet, D. H.; McCook, G. P.; Dorren, J. D.;
   Johansson, S.; Sahade, J.
Bibcode: 1990ESASP.310..383G
Altcode: 1990eaia.conf..383G
  No abstract at ADS

Title: Fe II lines from laboratory and astrophysical sources.
Authors: Baschek, B.; Johansson, S.
Bibcode: 1990JQSRT..44..215B
Altcode:
  No abstract at ADS

Title: High Resolution Ultraviolet Stellar Spectroscopy From Space
    Observatories - Atomic Physics and Astrophysics
Authors: Leckrone, D. S.; Johansson, S.; Kurucz, R. L.; Adelman, S. J.
Bibcode: 1989BAAS...21.1198L
Altcode:
  No abstract at ADS

Title: Complex atoms in astrophysical spectra.
Authors: Johansson, S.; Cowley, C. R.
Bibcode: 1988JOSAB...5.2264J
Altcode: 1988OSAJB...5.2264J
  The paper reviews the spectroscopic work on atomic lines and energy
  levels in neutral and singly and doubly ionized iron-group elements
  during the past 35 years. The completeness of the analysis of these
  spectra was graded and they were compared with the data included in
  the multiplet tables of Moore (1962, 1972). Specific comments are
  given on each spectrum. New demands for atomic data resulting from
  high-resolution spectroscopy of peculiar stars and observations from
  above the earth's atmosphere are discussed. The atomic data that have
  become available since Moore's compilations are referred to here as
  second-generation spectra.

Title: Absorption spectra of Fe I in the 1550 - 3215-Å region.
Authors: Brown, C. M.; Ginter, M. L.; Johansson, S.; Tilford, S. G.
Bibcode: 1988JOSAB...5.2125B
Altcode: 1988OSAJB...5.2125B
  The high-dispersion absorption spectrum of Fe I is reported in the
  1550-3215-A region. Included are wavelengths of about 3000 observed
  spectral features, improved spectral assignments, 248 new energy
  levels, and a value for the ionization potential of 63 737/cm obtained
  from extrapolation of Rydberg series. Improved wavelengths for several
  hundred V I and Ti I spectral lines determined on the same spectrograms
  as the iron data also are presented.

Title: Doubly Excited Feii Lines in the A-Star 21-PEGASI
Authors: Adam, J.; Baschek, B.; Brage, T.; Nilsson, A. E.; Johansson,
   S.
Bibcode: 1988ASSL..138..243A
Altcode: 1988IAUCo..94..243A; 1988pffl.proc..243A
  The majority of about 120 ultraviolet iron lines, among them strong
  lines around 1850 Å, which have recently been identified as transitions
  from doubly excited levels in Fe II during a new investigation of the
  hollow-cathode spectrum of iron, coincide with absorption lines in the
  high-resolution IUE spectrum of the sharp-lined A star 21 Pegasi. Model
  atmosphere calculations of the line strengths confirm the identification
  for about one third of the lines.

Title: Accidental Degeneracy Between Doubly Excited States in Feii
Authors: Brage, T.; Nilsson, A. E.; Johansson, S.; Baschek, B.;
   Adams, J.
Bibcode: 1988ASSL..138...63B
Altcode: 1988IAUCo..94...63B; 1988pffl.proc...63B
  No abstract at ADS

Title: Future Laboratory Work in Feii
Authors: Johansson, S.
Bibcode: 1988ASSL..138..313J
Altcode: 1988pffl.proc..313J; 1988IAUCo..94..313J
  No abstract at ADS

Title: On regularities in complex spectra of iron group elements
    and their dominance in stellar spectra
Authors: Johansson, S.
Bibcode: 1987PhyS...36...99J
Altcode:
  Regularities in complex spectra of iron group elements are
  illustrated as regards iso-electronic and iso-ionic sequences as
  well as iso-elemental comparisons. Determination of series limits and
  ionization potentials in spectra of doubly ionized iron-group elements
  from iso-ionic plots and Ritz diagrams is discussed. New data for
  doubly-excited states in Fe I are deduced from iso-ionic regularities
  in the binding energy of two-electron configurations nl<SUP>2</SUP>
  relative to a core of d-electrons. New spectroscopic data for Fe I
  are presented together with a discussion of the dominance of the Fe
  I spectrum in the sun.

Title: Ultraviolet Doubly Excited Fe II Lines in the Laboratory and
    in the A-Type Star 21 Pegasi
Authors: Adam, J.; Baschek, B.; Johansson, S.; Nilsson, A. E.;
   Brage, T.
Bibcode: 1987ApJ...312..337A
Altcode:
  During a new investigation of the UV hollow-cathode spectrum of iron,
  some 120 lines were identified, among them strong lines around 1850 A,
  as transitions from doubly excited levels in Fe II. A combination of
  selective population by charge-transfer processes in the laboratory
  source and of a strong configuration interaction is probably the cause
  of unexpectedly large intensities of a great number of lines. The
  new energy levels and calculated oscillator strengths for the newly
  identified transitions are presented. Most of the new lines coincide
  with absorption lines in the high-resolution IUE spectrum of the
  sharp-lined A star 21 Pegasi. For about one-third of them, located
  mostly in the region 1750-1900 A, the identifications are confirmed
  by modal atmosphere calculations. For the remaining coincidences the
  stellar line is probably blended with another contributor.

Title: The absorption spectrum of titanium between 1900 Å and 2315 Å
Authors: Forsberg, P.; Johansson, S.; Smith, P. L.
Bibcode: 1986PhyS...34..759F
Altcode:
  The absorption spectrum of Ti I has been analyzed in the region
  1900-2315 A. The list contains 219 lines, of which 64 have been
  identified as transitions between the ground term and terms of the odd
  configurations (3d + 4s)3 np (n = 4, 5). Sixteen new energy levels
  have been found, and three odd level values have been revised. Most
  of the identified Ti I lines are present in the solar spectrum.

Title: The identification of high-level transitions of Fe II in
    stellar spectra.
Authors: Johansson, S.; Cowley, C. R.
Bibcode: 1984A&A...139..243J
Altcode:
  Positive identifications are made in four
  B and A-type stellar spectra of lines from
  3d<SUP>6</SUP>(<SUP>5</SUP>D)4d-3d<SUP>6</SUP>(<SUP>5</SUP>D)4f
  transitions in Fe II. The lowest levels of the 4d terms have
  excitation energies of 10.3 eV, while those of the 4f terms are at
  12.8 eV. Numerous features that were previously unidentified in B and
  A stars may now be explained. The obvious presence of such transitions
  makes it probable that many other high-level transitions are present in
  stellar spectra. Some of these transitions have not yet been identified
  in laboratory studies analyses, but they could be of considerable
  importance in the chemical analyses of stellar atmospheres.

Title: Selective excitation of Fe II in the laboratory and late-type
    stellaratmospheres.
Authors: Johansson, S.; Jordan, C.
Bibcode: 1984MNRAS.210..239J
Altcode:
  Low resolution spectra of cool giants and supergiants observed with the
  International Ultraviolet Explorer (IUE) satellite contain emission
  features for which it has been difficult to establish unambiguous
  identifications. High resolution spectra of RR Tel and Beta Gru
  (M 3 II) show lines which can be definitely attributed to Fe II. The
  presence of particular transitions and absence of others suggests that
  the source of excitation for levels with excitation energy around 10
  eV is emission in the H Ly alpha line which is strong and broad in
  the cool giants and supergiants. New laboratory spectra confirm the
  excitation route for Ly alpha pumping to a further 4G0 level at about
  13 eV, which decays to give the strong feature at 1870 A observed at
  low spectral resolution in several cool stars.

Title: New Fe II lines in IUE spectra of stars.
Authors: Johansson, S.
Bibcode: 1984ESASP.218..307J
Altcode: 1984iue..conf..307J
  The never-ceasing need for more atomic data of Fe II for astrophysical
  purposes is discussed in terms of present state and future work
  on the term analysis of this spectrum. More data already exist and
  an extended analysis of laboratory data has just started. Special
  excitation conditions in stars allow highly excited states to be
  populated for which data is needed. Some new presumptive interstellar
  lines are reported.

Title: Ultraviolet Spectroscopy of Cool Stars from IUE (invited Paper)
Authors: Jordan, C.; Judge, P.; Johansson, S.
Bibcode: 1984uxsa.coll...51J
Altcode: 1984IAUCo..86...51J; 1984uxsa.conf...51J
  No abstract at ADS

Title: A comparison between the observed and predicted Fe II spectrum
    in different plasmas.
Authors: Johansson, S.
Bibcode: 1984PhST....8...63J
Altcode: 1984PhyS....8...63J
  This paper gives a survey of the spectral distribution of emission
  lines of Fe II, predicted from a single atomic model. The observed
  differences between the recorded and the predicted spectrum are
  discussed in terms of deficiencies of the model and interactions within
  the emitting plasma. The author gives a number of illustrative examples
  of unexpected features with applications to astrophysics.

Title: Strong Fe II fluorescence lines in RR Tel and V1016 Cyg
    excited by C IV in a Bowen mechanism.
Authors: Johansson, S.
Bibcode: 1983MNRAS.205P..71J
Altcode:
  Ten strong lines in the IUE spectrum of RR Tel have been
  identified as transitions from a common upper level of Fe
  II, y<SUP>4</SUP>H<SUP>0</SUP><SUB>11/2</SUB>. The level is
  selectively populated through resonant photoexcitation from
  a<SUP>4</SUP>F<SUB>9/2</SUB> by one of the resonance lines of C IV,
  λ1548.2 Å. Five of these lines appear also in the spectrum of
  V1016 Cyg.

Title: Two CR II multiplets around 1430 A appearing in absorption
    in the spectrum of a solar active region
Authors: Johansson, S.
Bibcode: 1982MNRAS.201P..63J
Altcode:
  In a current analysis of Cr II two new multiplets have been identified
  around 1430 Å. The identification of 27 lines establishes the new
  terms y <SUP>6</SUP>F<SUP>0</SUP> and y <SUP>6</SUP>D<SUP>0</SUP>
  of the 3d<SUP>3</SUP> 4s 4p configuration by their combinations
  with 3d<SUP>4</SUP> 4s a <SUP>6</SUP>D. Most of the lines appear in
  absorption in the spectrum of a solar active region.

Title: Atomic Spectroscopy for Astrophysical Applications
Authors: Johansson, S.
Bibcode: 1981SSRv...29..387J
Altcode:
  The recent work in atomic spectroscopy at the Department of Physics,
  University of Lund, is briefly reviewed and some examples of application
  to astrophysics are presented.

Title: Beam-foil lifetime measurements of some Fe II energy levels
Authors: Johansson, S.; Litzen, U.; Lundin, L.; Mannervik, S.
Bibcode: 1981PhyS...24...30J
Altcode:
  The decay of 11 Fe II spectral lines in the region 2500-3200 A has been
  recorded with the beam-foil technique. The line-blending problem has
  been carefully studied, and the measurements have yielded lifetimes
  for 5 levels believed to be unaffected by blends. No previous lifetime
  measurements were reported for these levels.

Title: New Spectroscopic Data for the Iron Group Elements
Authors: Johansson, S.
Bibcode: 1981LIACo..23..229J
Altcode: 1981cpsu.conf..229J
  No abstract at ADS

Title: Absorption lines in upsilon Sgr identified as high-level
    transitions of Fe II.
Authors: Johansson, S.
Bibcode: 1978MNRAS.184..593J
Altcode:
  Summary. An analysis of the high configurations of Fe ii has led to
  the identification of some 100 absorption lines in the photographic
  infrared spectrum of V Sagittarii. Almost all these lines belong to
  the transition arrays 3d6 5s-3d6 5p, 3d6 5p-3d6 Sd, 3d6 Sp-3d6 6s
  and 3d64d-3d64f of Fe ii, where the lower levels have an excitation
  potential between 9.6 and 11.3 eV. Some of these high-level transitions
  are enhanced in the laboratory source because of accidental resonance
  charge-transfer.

Title: The spectrum and term system of Fe II.
Authors: Johansson, S.
Bibcode: 1978PhyS...18..217J
Altcode:
  The spectrum of singly ionized iron, Fe II, has been recorded in
  the wavelength regions 900-2200 Å and 4800-11200 Å by means of a
  pulsed hollow-cathode discharge. In the vacuum-ultraviolet region
  identifications are given for 1358 lines. The list for the region
  above 4800 Å contains 1564 observed lines, 1341 of which are
  identified. In the 2200-4800 Å range about 350 lines in the line
  list published by Dobbie in 1938 have been newly identified. On
  the basis of interferometric measurements made by G. Norlén
  of 350 lines a recalculation of the whole term system has been
  performed. Altogether 576 energy levels are now known in Fe II,
  some 250 of which are the results of the present analysis. The
  levels belong to the configurations (3d<SUP>6</SUP>)4s, 5s, 6s,
  4p, 5p, 3d, 4d, 5d, 4f and (3d<SUP>5</SUP>4s)4s, 5s, 4p, 4d and
  3d<SUP>5</SUP>4p<SUP>2</SUP>. Theoretical predictions of the structure
  of the (3d<SUP>6</SUP>4p + 3d<SUP>6</SUP>5p + 3d<SUP>5</SUP>4s4p)
  complex by J. Sinzelle and J. F. Wyart are in good agreement with the
  observations. The ionization energy has been determined to 130 563 ±
  10 cm<SUP>-1</SUP>.

Title: New Fe II identifications in the infrared spectrum of Eta
    Carinae.
Authors: Johansson, S.
Bibcode: 1977MNRAS.178P..17J
Altcode:
  Summary. An extended analysis of the Fe ii spectrum, based on new
  observations in the infrared, has led to the identification of about
  50 lines in the infrared spectrum of Eta Carinae. More than half of
  the lines belong to the 3d6 5s-3d6 Sp transition array.

Title: The Finnish-Swedish laser project
Authors: Johansson, S.; Paunonen, M.; Sharma, A.
Bibcode: 1975lti..proc..120J
Altcode:
  The design and operation of a laser satellite rangefinder are
  described. The design parameters of the system are outlined, and
  directional calibration is discussed. The transmitter is based on a
  Pockels-cell Q-switched ruby-laser configuration with pulse slicing
  and amplification stages. The receiver consists of an astronomical
  telescope with a parabolic mirror and a photomultiplier installed at
  the prime focus. Timing is accomplished using a quartz clock system
  synchronized with the Universal Time Scale by a LORAN phase-locked
  frequency-comparison receiver.

Title: Analysis of 4d-4f transitions in Fe II.
Authors: Johansson, S.; Litzen, U.
Bibcode: 1974PhyS...10..121J
Altcode:
  The Fe II-spectrum emitted from a pulsed hollow cathode has been
  investigated in the region 4 800-11 500 Å. As a first result of
  the analysis 481 lines have been identified as belonging to the
  3d<SUP>6</SUP>(<SUP>5</SUP>D)4d-3d<SUP>6</SUP> (<SUP>5</SUP>D)4f
  transition array. The term structure shows good agreement with
  predictions by R. D. Cowan.

