| 1. |
- Dubernet, M. L., et al.
(författare)
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The virtual atomic and molecular data centre (VAMDC) consortium
- 2016
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:7
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Tidskriftsartikel (refereegranskat)abstract
- The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Albert, Damien, et al.
(författare)
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A Decade with VAMDC : Results and Ambitions
- 2020
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&M data from more than one database. Finally, we present our vision for the future of VAMDC.
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| 7. |
- Biemont, E, et al.
(författare)
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Core-polarization effects and radiative lifetime measurements in PrIII
- 2001
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 64:2
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Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes of eight levels in Pr III have been measured using the time-resolved laser-induced fluorescence method. A tunable frequency-doubled dye laser with 1-ns pulse duration was used to excite selectively doubly ionized praseodymium in a laser-produced plasma. The experimental results agree generally well with theoretical data, provided core-polarization effects are considered in the calculations in an adequate way.
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| 8. |
- Biemont, E, et al.
(författare)
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Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII
- 2001
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:10, s. 1869-1876
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Tidskriftsartikel (refereegranskat)abstract
- The analysis of the spectrum of Yb rn has been extended allowing us to establish 11 new energy level values. In addition, radiative lifetimes of two excited states of Yb III have been measured for the first time using time-resolved laser-induced fluorescence following two-photon excitation. The good agreement between experimental results and semi-empirical calculations performed with the relativistic Hartree-Fock method including core-polarization effects allows the determination of transition probabilities for 15 lines.
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| 9. |
- Biemont, E, et al.
(författare)
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Radiative lifetime measurements and transition probabilities of astrophysical interest in ErIII
- 2001
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 321:3, s. 481-486
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of seven excited states of Er iii have been measured using time-resolved laser-induced fluorescence following two-photon excitation. Relativistic Hartree-Fock calculations taking core-polarization effects into account are found to be in excellent agreement with the experimental results. A large set of new calculated transition probabilities is presented for many transitions of astrophysical interest. These results will be useful for investigating the composition of chemically peculiar stars.
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| 10. |
- Li, Z. S, et al.
(författare)
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Radiative lifetime measurements in TmIII with time-resolved laser spectroscopy and comparisons with HFR calculations
- 2001
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:8, s. 1349-1359
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Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes of eight levels in Tm m were measured with the time-resolved laser-induced fluorescence (LIF) technique. Free doubly ionized thulium ions were obtained in a laser-produced plasma. Three even-parity levels were excited from the ground state with one-photon excitation, using a laser system generating pulses of 1 ns duration. Five odd-parity levels were excited from the ground state with two-photon excitation, where a picosecond laser system was employed. In both cases, the lifetimes were evaluated from transient LIF signals detected with a fast-detection system. The experimental lifetime results were compared with Hartree-Fock calculations including relativistic corrections. Good agreement was achieved for the 4f(12)6p levels while larger discrepancies are noted for some 4f(12)5d levels.
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| 11. |
- Biemont, E, et al.
(författare)
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Doubly ionized thorium: Laser lifetime measurements and transition probability determination of interest in cosmochronology
- 2002
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 567:2, s. 1276-1283
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Tidskriftsartikel (refereegranskat)abstract
- The first lifetime measurements have been performed for six levels of doubly ionized thorium, an important cosmochronometer in astrophysics for estimating the age of the Galaxy. The levels, belonging to the 5f(2), 5f7p, 7s7p, and 6d7p configurations of Th III, have been measured by the time-resolved laser-induced fluorescence method and compared with relativistic Hartree-Fock calculations including configuration interaction and core-polarization effects. Taking advantage of the excellent agreement between theory and experiment, a first set of transition probabilities of astrophysical interest has been deduced for this ion from a combination of the experimental lifetimes and of the theoretical branching fractions.
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| 12. |
- Biemont, E., et al.
(författare)
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Lifetime measurements and calculations in Y+ and Y2+ ions
- 2011
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 414:4, s. 3350-3359
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Tidskriftsartikel (refereegranskat)abstract
- We report a new set oftheoretical transition probabilities in Y II, obtained using a multiconfiguration relativistic Hartree-Fock method including core polarization. The overall quality of the calculations is assessed by comparisons with new and previous lifetime measurements. In this paper, we report new measurements of five lifetimes in the 4d5p and 5s5p configurations, in the energy range of 32 048-44 569 cm(-1), obtained by the time-resolved laser-induced fluorescence method. A similar theoretical model, applied to Y III, leads to results in good agreement with new laser measurements of two 5p levels obtained in this work and with previous beam-foil results for 5d and 6s levels. An extensive set of oscillator strengths is also proposed for Y III.
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| 13. |
- Biemont, E, et al.
(författare)
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Lifetime measurements for doubly ionized uranium
- 2002
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:7, s. 1701-1705
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Tidskriftsartikel (refereegranskat)abstract
- The first lifetime measurements for doubly ionized uranium are reported in the present work. They relate to five levels belonging to the configurations 5f(2)6d(2), 5f(2)6d7s and 5f(3)7p and have been obtained with a time-resolved laser-induced-fluorescence technique, the ions being produced by laser ablation of a uranium oxide target.
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| 14. |
- 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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| 15. |
- Biemont, E, et al.
(författare)
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Measurement of radiative lifetimes and determination of transition probabilities of astrophysical interest in HoIII
- 2001
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 328:4, s. 1085-1090
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of six levels belonging to the 4f(10)6p configuration of Ho III have been measured for the first time using the time-resolved laser-induced fluorescence method. They are compared with multiconfigurational pseudo-relativistic Hartree-Fock calculations. A very good agreement is found. Using the experimental lifetimes and theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for this ion.
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| 16. |
- 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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| 17. |
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| 18. |
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| 19. |
- 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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| 20. |
- 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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| 21. |
- 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
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
-
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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| 22. |
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| 23. |
- Hartman, H., et al.
(författare)
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Radiative data for highly excited 3d 8 4d levels in Ni II from laboratory measurements and atomic calculations
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 600
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d84d levels of astrophysical interest in singly ionized nickel. Methods. Radiative lifetimes of seven high-lying levels of even parity in Ni II (98 400-100 600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects. Results. A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194-520 nm depopulating even parity 3d84d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.
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| 24. |
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| 25. |
- Macheva, G, et al.
(författare)
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Radiative lifetimes and transition probabilities in Rh I
- 2015
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 450:1, s. 223-228
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 17 high-lying excited states in Rh I aremeasured using the time-resolved laser-induced fluorescence method. Out of these lifetimes, 13 are new and the remaining four confirm previous measurements. Furthermore, we report the first theoretical investigation of Rh I, where the radiative decay properties of all experimentally known levels below 47 000 cm−1 are calculated using a pseudo-relativistic Hartree–Fock method including core polarization effects. The theoretical calculations are found to be in very good agreement with the experimental results. A large set of new transition probabilities is presented for lines of astrophysical interest in the spectral range 2200–10 000 Å.
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| 26. |
- Malcheva, G., et al.
(författare)
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Radiative parameters of Nb i excited states
- 2011
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 412:3, s. 1823-1827
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 17 excited levels of Nb i, in the energy range 27 400-47 700 cm-1 (5p y 6D degrees(9/2), 5p x 6D degrees(7/2), 5p w 4G degrees(7/2,9/2,11/2), 5s5p v 4D degrees(1/2,3/2,5/2,7/2), 5s6p n 4D degrees(1/2,3/2,5/2,7/2), 5s6p o 4F degrees(3/2,5/2,7/2,9/2)), have been measured. For 15 of these levels, the lifetimes are obtained for the first time. The lifetimes were measured using the time-resolved laser-induced fluorescence technique and the experiments are complemented by a theoretical investigation using a relativistic Hartree-Fock method including core polarization. By combining the experimental lifetimes and the calculated branching fractions, we obtain transition probabilities for the individual de-excitation channels from the investigated levels.
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| 27. |
- Nilsson, H., et al.
(författare)
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Experimental and theoretical lifetimes and transition probabilities for spectral lines in Nb II
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We have measured and calculated lifetimes of high lying levels in Nb II, and derived absolute transition probabilities by combining the lifetimes with experimental branching fractions. Methods. The lifetimes were measured using time-resolved laser-induced fluorescence in a two-photon and two-step excitation scheme. The branching fractions were measured in intensity calibrated spectra from a hollow cathode discharge, recorded with a Fourier transform spectrometer. The calculations were performed with the relativistic Hartree-Fock method including core polarization. Results. We report experimental lifetimes of 13 levels in the 4d(3)(F-4)5d and 4d(3)(F-4)6s subconfigurations, at an energy around 70 000 cm(-1). By combining the lifetimes with experimental branching fractions absolute transition probabilities of 59 lines are derived. The experimental results are compared with calculated values.
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| 28. |
- Nilsson, H., et al.
(författare)
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Experimental and theoretical lifetimes and transition probabilities for spectral lines in NbII
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. We have measured and calculated lifetimes of high lying levels in Nb II, and derived absolute transition probabilities by combining the lifetimes with experimental branching fractions. Methods. The lifetimes were measured using time-resolved laser-induced fluorescence in a two-photon and two-step excitation scheme. The branching fractions were measured in intensity calibrated spectra from a hollow cathode discharge, recorded with a Fourier transform spectrometer. The calculations were performed with the relativistic Hartree-Fock method including core polarization. Results. We report experimental lifetimes of 13 levels in the 4d3(4F)5d and 4d3(4F)6s subconfigurations, at an energy around 70 000 cm-1. By combining the lifetimes with experimental branching fractions absolute transition probabilities of 59 lines are derived. The experimental results are compared with calculated values.
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| 29. |
- 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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| 30. |
- Nilsson, Hampus, et al.
(författare)
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Transition probabilities of astrophysical interest in the niobium ions Nb+ and Nb2
- 2010
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We attempt to derive accurate transition probabilities for astrophysically interesting spectral lines of Nb II and Nb III and determine the niobium abundance in the Sun and metal-poor stars rich in neutron-capture elements. Methods. We used the time-resolved laser-induced fluorescence technique to measure radiative lifetimes in Nb II. Branching fractions were measured from spectra recorded using Fourier transform spectroscopy. The radiative lifetimes and the branching fractions were combined yielding transition probabilities. In addition, we calculated lifetimes and transition probablities in Nb II and Nb III using a relativistic Hartree-Fock method that includes core polarization. Abundances of the sun and five metal-poor stars were derived using synthetic spectra calculated with the MOOG code, including hyperfine broadening of the lines. Results. We present laboratory measurements of 17 radiative lifetimes in Nb II. By combining these lifetimes with branching fractions for lines depopulating the levels, we derive the transition probabilities of 107 Nb II lines from 4d(3)5p configuration in the wavelength region 2240-4700 angstrom. For the first time, we present theoretical transition probabilities of 76 Nb III transitions with wavelengths in the range 1430-3140 angstrom. The derived solar photospheric niobium abundance log epsilon(circle dot) = 1.44 +/- 0.06 is in agreement with the meteoritic value. The stellar Nb/Eu abundance ratio determined for five metal-poor stars confirms that the r-process is a dominant production method for the n-capture elements in these stars.
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| 31. |
- 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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| 32. |
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| 33. |
- 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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| 34. |
- 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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| 35. |
- Quinet, P., et al.
(författare)
-
Atomic data for VUV lines of astrophysical interest in singly ionized rhodium
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 184:3-6, s. 174-176
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Tidskriftsartikel (refereegranskat)abstract
- The first theoretical transition probabilities and oscillator strengths are reported for Rh II lines of astrophysical interest in the VUV region (100-200 nm). They have been obtained through the use of a pseudo-relativistic Hartree-Fock model including core-polarization effects and the accuracy has been estimated to be about 10-15% through a comparison with new experimental lifetimes measured using the time-resolved laser-induced fluorescence technique. (C) 2010 Elsevier B.V. All rights reserved.
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| 36. |
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| 37. |
- Quinet, P., et al.
(författare)
-
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
-
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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| 38. |
- Quinet, P., et al.
(författare)
-
Laser-induced-fluorescence lifetime measurements and relativistic Hartree-Fock oscillator strength calculations in singly ionized platinum
- 2008
-
Ingår i: Physical Review A. ; 77, s. 1-022501
-
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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| 39. |
- Quinet, P., et al.
(författare)
-
Oscillator strengths for lines of astrophysical interest in Rh II
- 2012
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. This work reports oscillator strengths for transitions of astrophysical interest in singly ionized rhodium. Methods. Seventeen radiative lifetimes in Rh+ have been measured with the time-resolved laser-induced fluorescence technique and combined with theoretical branching fractions calculated using a relativistic Hartree-Fock model including core-polarization effects to obtain oscillator strengths. Results. On the basis of the good agreement between theory and experiment for the lifetimes, new reliable oscillator strengths have been deduced for a set of 113 Rh II transitions in the spectral range 153-418 nm.
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| 40. |
- Quinet, P., et al.
(författare)
-
Oscillator strengths for lines of astrophysical interest in Rh II
- 2012
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537, s. A74-A74
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. This work reports oscillator strengths for transitions of astrophysical interest in singly ionized rhodium.Methods. Seventeen radiative lifetimes in Rh+ have been measured with the time-resolved laser-induced fluorescence technique and combined with theoretical branching fractions calculated using a relativistic Hartree-Fock model including core-polarization effects to obtain oscillator strengths.Results. On the basis of the good agreement between theory and experiment for the lifetimes, new reliable oscillator strengths have been deduced for a set of 113 Rh II transitions in the spectral range 153–418 nm.
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| 41. |
- Quinet, P, et al.
(författare)
-
Radiative lifetime measurements and transition probability calculations in lanthanide ions
- 2002
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Ingår i: Journal of Alloys and Compounds. - 0925-8388. ; 344:1-2, s. 255-259
-
Tidskriftsartikel (refereegranskat)abstract
- We have undertaken a systematic investigation of spectroscopic properties of lanthanide ions (Z=57-71). Using time-resolved laser-induced fluorescence following one- or two-photon excitations, a large number of radiative lifetimes have been measured at the Lund Laser Centre for singly, doubly and trebly ionized atoms. These new measurements have been used for testing theoretical calculations performed within the framework of a relativistic Hartree-Fock approach taking core-polarization effects into account. Using the experimental lifetimes (when available) and the theoretical branching fractions, a large number of transition probabilities, most of them of astrophysical interest, have been deduced and are stored in a new database (DREAM). Up to now, the results obtained concern the following ions: La2+, Ce2+, Ce2+, Pr2+, Ho2+, Er2+, Tm2+, Tm2+, Yb2+, Yb2+, Yb2+, Lu2+ and Lu2+. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 42. |
- Quinet, P, et al.
(författare)
-
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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| 43. |
- Storm, N., et al.
(författare)
-
3D NLTE modelling of Y and Eu : Centre-to-limb variation and solar abundances
- 2024
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 683
-
Tidskriftsartikel (refereegranskat)abstract
- Context: Abundances of s- and r-process elements in Sun-like stars constrain nucleosynthesis in extreme astrophysical events, such as compact binary mergers and explosions of highly magnetised rapidly rotating massive stars.Aims: We measure solar abundances of yttrium (Y) and europium (Eu) using 3D non-local thermal equilibrium (NLTE) models. We use the model to determine the abundance of Y, and also explore the model's ability to reproduce the solar centre-to-limb variation of its lines. In addition, we determine the Eu abundance using solar disc-centre and integrated flux spectra.Methods: We developed an NLTE model of Eu and updated our model of Y with collisional data from detailed quantum-mechanical calculations. We used the IAG spatially resolved high-resolution solar spectra to derive the solar abundances of Y across the solar disc and of Eu for integrated flux and at disc centre using a set of carefully selected lines and a 3D radiation-hydrodynamics model of the solar atmosphere.Results: We find 3D NLTE solar abundances of A(Y)(3D NLTE) = 2.30 ± 0.03stat ± 0.07syst dex based on observations at all angles and A(Eu) = 0.57 ± 0.01stat ± 0.06syst dex based on the integrated flux and disc-centre intensity. 3D NLTE modelling offers the most consistent abundances across the solar disc, and resolves the problem of severe systematic bias in Y and Eu abundances inherent to 1D LTE, 1D NLTE, and 3D LTE modelling.
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| 44. |
- Zhang, Zhiguo, et al.
(författare)
-
Experimental and theoretical studies of DyIII: radiative lifetimes and oscillator strengths of astrophysical interest
- 2002
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - 1365-2966. ; 334:1, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- The lifetimes of three short-lived levels belonging to the 4f(9) 6p configuration and of two long-lived levels of the 4f(9) 5d configuration of Dy iii have been measured for the first time using time-resolved laser-induced fluorescence techniques. They are in good agreement with theoretical values calculated within the framework of a pseudo-relativistic configuration interaction approximation. Using the experimental lifetimes and the theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for Dy III.
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| 45. |
- Zhang, Z. G, et al.
(författare)
-
Natural radiative lifetimes in Ce II
- 2001
-
Ingår i: Physica Scripta. Topical Issues. - 0281-1847. ; 63:2, s. 122-127
-
Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes of 18 levels (energy range between 30 000 cm(-1)) and 39 000 cm(-1), in Ce II have been measured using the time-resolved laser-induced fluorescence method. A tunable frequency-doubled dye laser with I ns pulse duration was used to excite selectively singly ionized cerium in a laser-produced plasma The experimental results are compared with theoretical data and the agreement is found to be very good.
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| 46. |
- Zhang, Zhiguo, et al.
(författare)
-
Measurement of lifetimes by laser-induced fluorescence and determination of transition probabilities of astrophysical interest in NdIII
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 385:2, s. 724-732
-
Tidskriftsartikel (refereegranskat)abstract
- Selective lifetime measurements by time-resolved laser-induced fluorescence spectroscopy for 5 levels belonging to the 4f(3)5d configuration of doubly ionized neodymium provide a first and useful experimental test of the relativistic Hartree-Fock calculations in this ion of astrophysical interest. As a consequence, the accuracy of the transition probabilities deduced in the present work is well assessed. These new data are expected to help astrophysicists in the future to refine the analysis of the composition of chemically peculiar stars which frequently show large overabundances of lanthanides when compared to the solar system standards.
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| 47. |
- Zhang, Zhiguo, et al.
(författare)
-
Radiative lifetime measurements and oscillator strengths of astrophysical interest in HoIII
- 2002
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 384:1, s. 364-370
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of three long-lived levels belonging to the 4f(10)5d configuration of Ho III have been measured, for the first time, using the time-resolved laser-induced fluorescence technique. A good agreement between the experimental lifetimes and theoretical results obtained within a multiconfigurational pseudo-relativistic Hartree-Fock (HFR) approach including core-polarization (CP) effects is observed provided an adequate scaling factor is applied to the <4f&VERBAR;r&VERBAR;5d> transition matrix element. From the comparison theory-experiment, it has been possible to assess the reliability of the oscillator strengths of the 4f-5d transitions of astrophysical interest, particularly for the lines depopulating the levels considered in the present work. The present results fill in a gap concerning the f-values of doubly ionized holmium and are needed for a quantitative evaluation of the holmium abundance in some peculiar stars.
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| 48. |
- Zhang, Zhiguo, et al.
(författare)
-
Time-resolved laser spectroscopy of multiply ionized atoms: natural radiative lifetimes in Ce IV.
- 2001
-
Ingår i: Physical Review Letters. - 1079-7114. ; 87:27 Pt 1, s. 273001-273001
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes have been measured for two excited levels of Ce IV using the time-resolved laser-induced fluorescence technique. Ce3+ ions were produced in a laser-induced plasma. In the measurements, a suitable magnetic field was applied to reduce the recombination between electrons and the ions and thus the background light from the recombination, and special care was exercised to avoid flight-out-of-view effects on the lifetime measurements for the high-velocity ions. The experimental lifetime results, tau = 30(2) ns for the level 49 737 cm(-1) and tau = 30(3) ns for the level 52 226 cm(-1), were compared with relativistic Hartree-Fock calculations (tau = 30.5 and 30.0 ns) indicating a particularly excellent agreement.
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| 49. |
- Biemont, E, et al.
(författare)
-
Experimental lifetime determination in neutral praseodymium (Pr I) and neodymium (Nd I)
- 2004
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:7, s. 1381-1389
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 18 even-parity levels of Pr I and 15 odd-parity levels of Nd I. The new results are compared with the few experimental data available in the literature and good agreement is found. However, fragmentary knowledge of the spectra prevents reliable calculation of branching fractions and calls for additional laboratory efforts in order to provide the astrophysicists with reliable transition probabilities needed for investigating the magnetic fields in chemically peculiar stars.
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| 50. |
- Biemont, E, et al.
(författare)
-
Lifetime measurements and calculations in LaI
- 2004
-
Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 30:2, s. 157-162
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 20 odd-parity levels of La I belonging to the configurations 5d(2)6p, 5d6s6p and 4f5d6s. The new results are compared with the few experimental data available in the literature and with theoretical calculations including configuration interaction effects. The agreement theory-experiment is generally satisfying but discrepancies are observed for some levels emphasizing the difficulty to get a reliable theoretical model in such a heavy and complex neutral element.
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