| 1. |
- Biémont, E, et al.
(författare)
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Radiative lifetime and oscillator strength determinations in Sm III
- 2003
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 399:1, s. 343-349
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 6 levels belonging to the4f5(6Hdeg,6Fdeg)5d configuration of Sm III have beenmeasured for the first time using a time-resolved laser-inducedfluorescence technique. Experimental data have been compared withsemi-empirical calculations. The agreement is excellent for 4 levelswith 6Fdeg as a parent term. Larger discrepancies(53 and 37) are observed for 2 levels with 6Hdegand 6Fdeg, respectively, as a parent term and areexplainable by strong mixing and cancellation effects occurring in theline strength calculations which are responsible of instabilitiesoccurring in the lifetimes considered as a function of J value withinthe term. Branching ratios for the lines depopulating the levels ofinterest have been measured by Fourier transform spectroscopy. A firstset of oscillator strengths has been deduced for this ion.
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| 2. |
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| 3. |
- Dolk, Linus, et al.
(författare)
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The laboratory analysis of Bi II and its application to the Bi-rich HgMn star HR 7775
- 2002
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 388:2, s. 692-703
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Tidskriftsartikel (refereegranskat)abstract
- The bismuth spectrum emitted from a hollow cathode discharge has been recorded with a Fourier Transform Spectrometer (FTS). Accurate wavelengths have been determined for 104 lines, and several new energy levels have been found, while the accuracy of previously known level energies have been improved. The hyperfine structure of all observed lines has been analyzed, yielding hyperfine constants A and B for 56 levels. With the aid of the laboratory measurements the optical region spectrum of the HgMn star HR 7775 has been studied for all observable lines. The wavelengths and hfs constants established from the laboratory work have been combined with theoretical gf values to identify spectral lines and make an abundance estimation of bismuth. It has been established that bismuth is present in HR 7775 at an enhancement level of approximately 5 orders of magnitude relative to the meteoritic abundance, consistent with previous observations in the ultraviolet region of this star. Astrophysical gf values are presented for a number of lines.
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| 4. |
- Dolk, Linus, et al.
(författare)
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The presence of Nd and Pr in HgMn stars
- 2002
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 385:1, s. 111-130
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Tidskriftsartikel (refereegranskat)abstract
- Optical region spectra for a number of upper main sequence chemically peculiar (CP) stars have been observed to study singly and doubly ionized praseodymium and neodymium lines. In order to improve existing atomic data of these elements, laboratory measurements have been carried out with the Lund VUV Fourier Transform Spectrometer (FTS). From these measurements wavelengths and hyperfine structure (hfs) have been studied for selected , and lines of astrophysical interest. Radiative life times for some excited states of have been determined with the aid of laser spectroscopy at the Lund Laser Center (LLC) and have been combined with branching fractions measured in the laboratory to calculate gf values for some of the stronger optical lines of . With the aid of the derived gf values and laboratory measurements of the hfs, a praseodymium abundance was derived from selected lines in the spectrum of the Am star 32 Aqr. This abundance was used to derive astrophysical gf values for selected lines in 32 Aqr, and these gf values were used to get a praseodymium abundance for the HgMn star HR 7775. The praseodymium abundance in HR 7775 was then utilized to derive astrophysical gf values for all observable lines in this star. The neodymium abundance, derived from unblended lines of in HR 7775, has been utilized to establish astrophysical gf values for observed lines in the optical region of this star. Selected and lines have been identified and studied in a number of HgMn stars and three hot Am stars. The praseodymium and neodymium abundance change rapidly from an approximate 1-1.2 dex enhancement for the hot Am stars to 1.5-3 dex enhancement for the cool HgMn stars, indicating a well-defined boundary between the hot Am and HgMn stars in the vicinity of 10 500 K. The enhancement of praseodymium and neodymium in Am and HgMn stars may be explained by diffusive processes active in the stellar atmosphere, while the observed discontinuity might be explained by a thin hydrogen convection zone thought to be present for the Am stars, but absent in the HgMn stars. The absence of a convection zone would cause the diffused elements to gather higher in the atmosphere of HgMn stars compared to Am stars, and explain the observed increase in abundance.
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| 5. |
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| 6. |
- Eriksson, Mattias, et al.
(författare)
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Spectral Data for Ta II with Application to the Tantalum Abundance in chi Lupi
- 2002
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Ingår i: Physica Scripta. - 0031-8949. ; 65:6, s. 480-489
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Tidskriftsartikel (refereegranskat)abstract
- Tantalum spectra, emitted from a hollow cathode, have been recorded with a Fourier transform spectrometer in the region 2000–5000 Ů The observed hyperfine patterns of Ta II have been analyzed, yielding center-of-gravity wavelengths for 199 lines and hyperfine constants for 38 even and 97 odd levels of Ta II. Improved energy level values have been derived. The laboratory data have been used for a study of the tantalum abundance of the CP star chi Lupi.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Gullberg, Dag, et al.
(författare)
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Accurately Measured Wavelengths of Zn I and Zn II Lines of Astrophysical Interest
- 2000
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Ingår i: Physica Scripta. - 0031-8949. ; 61:6, s. 652-656
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Tidskriftsartikel (refereegranskat)abstract
- Zinc is an element of importance in many research fields within astronomy and astrophysics, from cosmology to stellar atmosphere dynamics. With the aim of improving three decades old measurements of zinc lines of astrophysical interest, emission spectra of Zn I and Zn II have been recorded using a Fourier Transform Spectrometer with a hollow cathode light source. Revised energies for previously known levels are derived from the measurements for Zn I 3d104snl and for Zn II 3d10nl and 3d94s2. Isotope shifts are observed in Zn II lines involving the 3d94s2 configuration. The accuracy of prominent lines and energy levels are about 0.001-0.003 cm-1 and 0.002-0.005 cm-1 respectively.
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| 12. |
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| 13. |
- Isberg, Bengt, et al.
(författare)
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Revised and extended analysis of Ga II
- 1985
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Ingår i: Physica Scripta. - 0031-8949. ; 31:6, s. 533-538
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Tidskriftsartikel (refereegranskat)abstract
- The gallium spectrum emitted from a hollow cathode has been recorded in the region 500-9800 A. 142 lines have been classified as transitions in Ga II. Energy levels have been derived from the observations, and perturbations within the n = 4 configuration complex are discussed. Besides the previously known mixing between 4s4d and 4p2, it has been found that the structure of 4s4/is strongly affected by interaction with 4p4d. The ionization limit has been determined to 165 465.8 cm-1.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Johansson, Sveneric, et al.
(författare)
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Experimental f-Value and Isotopic Structure for the Ni I Line Blended with [O I] at 6300 Å
- 2003
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 584:2, s. 107-110
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the oscillator strength of the Ni I line at 6300.34Å, which is known to be blended with the forbidden line [O I]lambda6300 used for the determination of the oxygen abundance in coolstars. We also give wavelengths of the two isotopic line components of58Ni and 60Ni derived from the asymmetriclaboratory line profile. These two line components of Ni I have to beconsidered when calculating a line profile of the 6300 Å featureobserved in stellar and solar spectra. We also discuss the labeling ofthe energy levels involved in the Ni I line since level mixing makes thetheoretical predictions uncertain.
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| 19. |
- Johansson, S. G, et al.
(författare)
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Comparison of New Experimental and Astrophysical F-values For Some Ru-ii Lines, Observed In Hst Spectra of Chi-lupi
- 1994
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 421:2, s. 809-815
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Tidskriftsartikel (refereegranskat)abstract
- We report on experimental absolute oscillator strengths for 18 UV lines of Ru II, obtained by combining laser-induced fluorescence measurements of radiative lifetimes and branching fractions from line intensities in a calibrated Fourier-transform spectrum. HST/GHRS observations of the spectrum of the sharp-lined B star chi Lupi contain six of these lines, for which ''astrophysical'' relative f-values have been determined. The agreement is within 0.10 dex for a Ru abundance of log N(Ru)/N(H) = -7.90, which is 2.3 dex above the solar abundance.
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| 20. |
- Johansson, Sveneric, et al.
(författare)
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Resonance lines of La III
- 1971
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Ingår i: Journal of the Optical Society of America. - 0093-5433. ; 61:10, s. 1427-1428
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Tidskriftsartikel (refereegranskat)
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| 21. |
- Johansson, Sveneric, et al.
(författare)
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The 4f2-4f5d Lines of Ce III
- 1972
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Ingår i: Physica Scripta. - 0031-8949. ; 6:2-3, s. 139-139
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Tidskriftsartikel (refereegranskat)
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| 22. |
- Johansson, Sveneric, et al.
(författare)
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The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
- 2002
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
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Konferensbidrag (refereegranskat)abstract
- 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 Šin detail.
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| 23. |
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| 24. |
- Johansson, Sveneric, et al.
(författare)
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The Term 4f8 7F in Gd III
- 1973
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Ingår i: Physica Scripta. - 0031-8949. ; 8:1-2, s. 43-43
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Tidskriftsartikel (refereegranskat)
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| 25. |
- Jupén, Christer, et al.
(författare)
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The 2p53s, 3p and 3d configurations in neon-like Ti XIII and Fe XVII
- 1984
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Ingår i: Physica Scripta. - 0031-8949. ; 30:2, s. 112-112
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Tidskriftsartikel (refereegranskat)abstract
- Spectra emitted from laser-produced plasmas of scandium, titanium, vanadium and chromium have been recorded in the region 270-600 Å, and lines belonging to the 3s-3p and 3p-3d transition arrays in neonlike ions have been identified. The 2p53s, 3p and 3d energy levels have been derived from the observations for Ti XIII and from solar flare lines for Fe XVII. Hartree-Fock calculations and parametric fits have yielded scaling factors for ab initio energy integrals that make it possible to predicts 3s-3p and 3p-3d wavelengths. Observed and predicted wavelengths for the strongest lines in Sc XII, V XIV, Cr XV and Ni XIX are presented.
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