| 1. |
- Biémont, E, et al.
(författare)
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Decay of metastable states in Nd II
- 2007
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Ingår i: The European physical journal D Atomic, molecular and optical physics. ; 41, s. 211-
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Biémont, É., et al.
(författare)
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Decay of metastable states in NdII
- 2007
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 41:2, s. 211-219
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Tidskriftsartikel (refereegranskat)abstract
- The difficulty associated with an accurate determination of transition rates for forbidden lines in lowly ionized heavy elements is illustrated in the case of Nd II. We have investigated the radiative decay of the low-lying metastable levels in Nd+ including the two levels 4f(4)(I-5) 5d K-6(11/2) and 4f(4)(I-5) 5d I-6(13/2). In these two particular cases, using di. erent theoretical approaches, we. nd that the decay is dominated by the M1 channels but that the E2 contributions are of the same order of magnitude. These levels have also been studied experimentally by lifetime measurements with the heavy ion storage ring CRYRING of Stockholm University. The difficulties encountered when performing such experiments are underlined and discussed.
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| 3. |
- Gurell, J., et al.
(författare)
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Laser-probing measurements and calculations of lifetimes of the 5d D-2(3/2) and 5d D-2(5/2) metastable levels in BaII
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Tidskriftsartikel (refereegranskat)abstract
- The two metastable levels 5d(2)D(3/2) and 5d(2) D-5/2 in Ba II both show extremely long lifetimes of the order of several tens of seconds each. This has been found both by experiments and by theoretical predictions. The small transition probabilities associated with these two levels make them interesting and challenging for theoreticians as well as for experimentalists. Several calculations and measurements of these two lifetimes have been made previously but discrepancies between the results are present. This article presents values of ??? = 89.4 +/- 15.6 s for the D-2(3/2) level and ??? = 32.0 +/- 4.6 s for the D-2(5/2) level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in ???= 82.0 s for the D-2(3/2) level and ???= 31.6 s for the D-2(5/2) level.
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| 4. |
- Lundin, P., et al.
(författare)
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Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99, s. 213001-
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Tidskriftsartikel (refereegranskat)abstract
- A laser probing investigation has yielded the lifetimes of the 3s23p4(1D)3d 2G7/2,9/2 metastable doublet states of Ar+. The results, obtained with the CRYRING ion storage ring of Stockholm, are 3.0±0.4 and 2.1±0.1 s, respectively. Comparisons with theoretical values calculated with two independent theoretical approaches, i.e., the pseudorelativistic Hartree-Fock method and the multiconfiguration Breit-Pauli approach, have allowed us to establish the unexpected and extraordinary strong contribution of an electric octupole (E3) transition to the ground state, in addition to the M1 decay channels to the 3d 2,4F states and the E2 contributions to the 4s 2P, 2D states.
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| 5. |
- Biemont, E, et al.
(författare)
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Lifetimes along perturbed Rydberg series in neutral thallium
- 2005
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:19, s. 3547-3558
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 15 Tl I levels belonging to the 6s(2)ns(2)S(1/2) (n = 7-14) and 6s(2)nd(2)D(3/2) Rydberg series (n = 6-12) have been measured using a time-resolved laser-induced fluorescence technique. All the measured levels have been excited from the ground state 6s(2)6p(2)P(1/2)(0) (odd parity) with a single-step excitation process. The general perturbation of the ns series by the 6s6p(2) configuration and the corresponding modification of the lifetimes are adequately reproduced by a theoretical model including core-polarization effects and combined with a least-squares fit to the observed energy levels. The general behaviour of the lifetime values for the 6s(2)np odd levels along the Rydberg series is also well reproduced. The use of the multiconfiguration quantum defect theory has allowed us to obtain lifetime values along the 6s(2)ns(2)S(1/2) series up to levels with n = 31.
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| 6. |
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| 7. |
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| 8. |
- Fivet, V, et al.
(författare)
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Radiative lifetimes and transition probabilities in TaI
- 2006
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 37:1, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 14 odd-parity Ta I levels, belonging to the 5d(3)6s6p and 5d(4)6p configurations in the energy range from 30 664 to 45 256 cm(-1). have been measured using the time-resolved laser-induced fluorescence technique. Extensive calculations, taking configuration interactions and corepolarisation effects into account, are able to reproduce in a satisfying way the available experimental results but suffer from the rather fragmentary knowledge of the level structure of this atom. New transition probabilities are deduced for a set of strong lines depopulating the levels investigated experimentally in the present work.
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| 9. |
- Fivet, V., et al.
(författare)
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Transition probabilities and lifetimes for atoms and ions from the sixth row of the periodic table and the database DESIRE
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 156, s. 250-254
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Tidskriftsartikel (refereegranskat)abstract
- We have started a systematic investigation of the radiative properties of the elements of the sixth row of the periodic table. Using a combination of experimental radiative lifetimes obtained with the time-resolved laser-induced fluorescence (LIF) technique and of theoretical branching fractions (BF) calculated with a HFR approach taking configuration interaction and core-polarization effects into account, transition probabilities have been deduced for a number of transitions of astrophysical interest. So far results have been obtained for the elements Ta, Re, Os, Ir, Tl or An or their ions. The results obtained are stored in the database DatabasE for the SIxth Row Elements (DESIRE), an extension of the database DREAM, which will be progressively created on a web site of the University of Mons-Hainaut in Belgium. In the present paper, some emphasis is put on the procedures followed to obtain the new results but also on the difficulties associated with their determination. (c) 2006 Elsevier B.V. All rights reserved.
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| 10. |
- Gurell, Jonas, 1981-, et al.
(författare)
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Laser-probing measurements and calculations of lifetimes of the 5d 2D3/2 and 5d 2D5/2 metastable levels in Ba II
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Tidskriftsartikel (refereegranskat)abstract
- The two metastable levels 5d 2D3∕2 and 5d 2D5∕2 in Ba II both show extremely long lifetimes of the order of several tens of seconds each. This has been found both by experiments and by theoretical predictions. The small transition probabilities associated with these two levels make them interesting and challenging for theoreticians as well as for experimentalists. Several calculations and measurements of these two lifetimes have been made previously but discrepancies between the results are present. This article presents values of τ=89.4±15.6 s for the 2D3∕2 level and τ=32.0±4.6 s for the 2D5∕2 level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in τ=82.0 s for the 2D3∕2 level and τ=31.6 s for the 2D5∕2 level.
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| 11. |
- Nilsson, Hampus, et al.
(författare)
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Lifetime measurements and transition probability calculations in singly ionized tungsten (W II)
- 2008
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 49:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- New measurements of radiative lifetimes for 9 levels in singly ionized tungsten (W II) have been performed with the time-resolved laser-induced-fluorescence technique. Transition probabilities have been obtained from a combination of experimental lifetimes and theoretical branching fractions. The reliability of the present results is assessed through the good agreement observed between the calculated lifetimes and the experimental values from this work and from previous publications. These new results fill in a gap in the available data for this atomic species particularly important for fusion reactors.
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| 12. |
- Palmeri, P., et al.
(författare)
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Lifetime measurements and calculated transition probabilities in W III
- 2008
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 78:1
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Tidskriftsartikel (refereegranskat)abstract
- New experimental lifetimes for two levels in doubly ionized tungsten, W III, have been obtained using the time-resolved laser-induced-fluorescence technique. Theoretical oscillator strengths obtained from a HFR calculation including the effects of core-polarization are reported for all transitions from levels below E < 70000 cm(-1) and with log g f >= -2, thus greatly extending our knowledge of the radiative data in W III. Good agreement is found between the calculated lifetimes and the experimental values from this and previous works. These new results fill a gap in the available data for this ion which is expected to play an important role in fusion reactors.
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| 13. |
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| 14. |
- Palmeri, P., et al.
(författare)
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Radiative lifetime measurements and semi-empirical transition probability calculations in neutral rhenium
- 2006
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 74:3, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 11 odd-parity levels of neutral rhenium (Re I) were measured using time-resolved laser-induced fluorescence techniques. For ten levels, there were no previous results available. The new results have been used to assess the accuracy of calculations with a Hartree-Fock-plus-relativistic-corrections model that takes configuration interaction and core-polarization effects into account and they have allowed the deduction of reliable semi-empirical transition probabilities for 81 Re I lines.
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| 15. |
- Palmeri, P, et al.
(författare)
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Transition probabilities and lifetimes in singly ionized rhenium
- 2005
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 362:4, s. 1348-1352
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Tidskriftsartikel (refereegranskat)abstract
- Transition probabilities and radiative lifetimes have been obtained for 45 transitions of Re II using a combination of radiative lifetime values obtained with the laser-induced fluorescence technique ( seven levels) and theoretical branching fractions. This new set of results, concerning ultraviolet and visible lines, will be useful in the future for investigating the composition of chemically peculiar stars.
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| 16. |
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| 17. |
- Quinet, P., et al.
(författare)
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Branching fractions andAvalues in singly ionized tantalum (Ta II)
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 493:2, s. 711-719
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We report on the theoretical and experimental lifetimes of Ta II, and calculated branching fractions for selected transitions.Methods. The theoretical data are obtained by means of a relativistic Hartree-Fock method with detailed attention to correlation effects. The experimental lifetimes are measured with the time-resolved, laser-induced, fluorescence technique.Results. The calculated results are in good agreement with both previously known and new experimental lifetimes. New transition probabilities have been deduced for a set of Ta II transitions of astrophysical interest.
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| 18. |
- Quinet, P., et al.
(författare)
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Laser-induced-fluorescence lifetime measurements and relativistic Hartree-Fock oscillator strength calculations in singly ionized platinum
- 2008
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Ingår i: Physical Review A. ; 77, s. 1-022501
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of eight odd-parity states of Pt II, in the energy range from 51 408 to 64 388 cm−1, have been measured by means of the time-resolved laser-induced-fluorescence technique. Free, singly ionized platinum ions were obtained in a laser-produced plasma and a tunable laser with 1.5 ns duration pulse was used to selectively excite the Pt+ ions. The comparison of the experimental results with relativistic Hartree-Fock calculations emphasizes the importance of valence-valence correlation and of core-polarization effects in this complex ion. A new and extensive set of calculated oscillator strengths and transition probabilities is reported in the present paper.
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| 19. |
- Quinet, P, et al.
(författare)
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Transition probabilities and lifetimes in neutral and singly ionized osmium and the Solar osmium abundance
- 2006
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 448:3, s. 93-1207
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 12 levels of Os I and for 9 levels of Os II. For 9 levels of Os I and 4 levels of Os II, there were no previous experimental data available. From a comparison with new theoretical calculations, taking configuration interactions and core-polarization effects into account, it has been possible to deduce oscillator strengths for 129 transitions of Os I and 137 transitions of Os II of astrophysical interest appearing in the wavelength range 180.0-870.0 nm. These results have allowed us to revise the abundance of osmium in the solar photosphere (log epsilon(Os) = 1.25 +/- 0.11). The newly derived oscillator strengths have been applied as well to derive the osmium abundance in the carbon-rich metal-poor star HD 187861.
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| 20. |
- Fivet, V., et al.
(författare)
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Transition probabilities and lifetimes in gold (Au I and Au II)
- 2006
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:17, s. 3587-3598
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of three odd-parity levels of neutral gold (Au I) and one odd-parity level of singly ionized gold (Au II), measured using the time-resolved laser-induced fluorescence technique, have allowed the testing of the reliability of a relativistic Hartree-Fock model of the atomic structure taking configuration interaction and core-polarization effects into account. The importance of the inclusion of the latter effects in the calculations is emphasized. The laser-induced fluorescence lifetimes, combined with the theoretical branching fractions, have allowed us to deduce oscillator strengths for six 5d(9)6s(2)-5d(9)6s6p and 5d(10)6s-5d(9)6s6p transitions of Au I and for sixty-three 5d(9)6s-5d(9)6p, 5d(9)6p-5d(9)7s and 5d(10)-5d(9)6p UV transitions of Au II.
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| 21. |
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| 22. |
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| 23. |
- Malcheva, G, et al.
(författare)
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Radiative lifetimes and transition probabilities of astrophysical interest in ZrII
- 2006
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 367:2, s. 754-762
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 16 odd levels belonging to the 4d(2)5p configuration of Zr II have been measured using a time-resolved laser-induced fluorescence technique with a single-step excitation process either from the ground state or from metastable levels belonging to the 4d(2)5s and 4d(3) configurations. For 12 levels, there were no previous results available. The new experimental results and the lifetime values available in the literature have allowed to test a theoretical relativistic Hartree-Fock (HFR) model including core-polarization effects and to deduce transition probabilities for 242 transitions of astrophysical interest in the range 187.8-535.0 nm.
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| 24. |
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| 25. |
- Xu, Huailiang, et al.
(författare)
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Improved atomic data for iridium atom (Ir I) and ion (Ir II) and the solar content of iridium
- 2007
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073. ; 104, s. 52-70
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Tidskriftsartikel (refereegranskat)abstract
- From a combination of radiative lifetime measurements, performed with a time-resolved laser-induced fluorescence technique, for nine odd-parity levels of Ir I and four odd-parity levels of Ir II and branching fraction calculations, extended sets of transition probabilities have been derived for transitions of astrophysical interest. The new results are compared with the few experimental data available in the literature and a good agreement is found. They extend considerably the previous sets of transition probabilities available in the literature. Implications of the new results regarding the solar content of iridium are briefly discussed.
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