| 51. |
- Palmeri, P., et al.
(författare)
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Radiative lifetime measurements and semi-empirical transition probability calculations in neutral rhenium
- 2006
-
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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| 52. |
- Palmeri, P, et al.
(författare)
-
Transition probabilities and lifetimes in singly ionized rhenium
- 2005
-
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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| 53. |
- 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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| 54. |
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| 55. |
- Quinet, P., et al.
(författare)
-
Branching fractions andAvalues in singly ionized tantalum (Ta II)
- 2008
-
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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| 56. |
- 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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| 57. |
- Quinet, P., et al.
(författare)
-
Oscillator strengths for lines of astrophysical interest in Rh II
- 2012
-
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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| 58. |
- 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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| 59. |
- 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
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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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| 60. |
- Quinet, P, et al.
(författare)
-
Transition probabilities and lifetimes in neutral and singly ionized osmium and the Solar osmium abundance
- 2006
-
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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| 61. |
- Schef, P, et al.
(författare)
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Disentanglement of magnetic field mixing reveals the spontaneous M2 decay rate for a metastable level in Xe
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:2, s. 020501-
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the radiative decay of the metastable level 5d(4)D(7/2) in Xe+. Theoretically we find the decay to be heavily dominated by an M2 transition and not by M1/E2 transitions. Lifetime measurements of 5d(4)D(7/2) in a storage ring are difficult since magnetic mixing of the metastable with a short-lived level quenches its population. Decay rates were determined at different magnetic field strengths (B) in order to allow a nonlinear extrapolation to B=0. The experimental lifetime of 2.4 +/- 0.8 s was in agreement with the calculated value, but much smaller than previously estimated.
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| 62. |
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| 63. |
- Schef, P, et al.
(författare)
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Lifetimes of metastable levels in Ar II
- 2004
-
Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 29:2, s. 195-199
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Tidskriftsartikel (refereegranskat)abstract
- We report on a calculation of five lifetimes of metastable levels in Ar II, obtained with a relativistic Hartree-Fock method in which most of the intravalence correlation is represented within a configuration interaction scheme while core-valence correlation is described by a core-polarization model potential with a core-penetration corrective term. The quality of the calculation has been assessed through an experimental determination of the radiative lifetime of the metastable 3d(4)F(9/2) level. The experiment was performed with a laser probing technique on a stored ion beam at the CRYRING of Stockholm.
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| 64. |
- Xu, Huailiang, et al.
(författare)
-
Radiative lifetime and transition probabilities in CdI and CdII
- 2004
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 70:4
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 11 levels belonging to the 5s5p P-1(1)o 5snd D-3(1,2) (n=6-9) and 5sns S-3(1) (n=7,8) series of Cd I, and of 5 levels of Cd II (i.e., 4d(10)5p P-2(1/2.3/2)o, 4d(10)6s S-2(1/2), and 4d(10)5d D-2(3/2,5/2)) have been measured using the time-resolved laser-induced fluorescence technique. Free neutral and singly ionized cadmium atoms have been generated by laser ablation. Single- or two-step excitation processes were considered to populate the levels under study. Branching fractions of Cd II transitions have been measured by laser-induced breakdown spectroscopy. Transition probabilities and oscillator strengths for Cd I and Cd II spectral lines originating from the above states as well as from the 4d(9)5 s(22)D(3/2,5/2) states of Cd II have been deduced by combining the experimental lifetimes and theoretical branching fractions obtained in multiconfigurational relativistic Hartree-Fock calculations taking core-polarization effects into account.
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| 65. |
- Xu, Huailiang, et al.
(författare)
-
Radiative lifetime measurements in ErII by time-resolved laser spectroscopy
- 2003
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:9, s. 1771-1781
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of 30 excited states of Er 11, ranging in energy from 25 592 to 36 148 cm(-1), have been measured by means of a time-resolved laser-induced fluorescence (LIF) technique. Free, singly ionized erbium ions were produced in a laser-induced plasma. A tunable laser, with 1 ns duration pulse, was employed to selectively excite the Er+ ions. The lifetime values were evaluated from the transient LIF signals recorded by a fast detection system. A comparison of the new results with previously published values is given. HFR calculations, including core-polarization contributions, are found to be in reasonable agreement with experiment, but the present calculations clearly indicate that further laboratory and theoretical work is urgently needed, particularly for the low lying odd configurations of this complex ion.
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| 66. |
- Xu, Huailiang, et al.
(författare)
-
Radiative lifetimes of Cd I and Cd II excited states
- 2003
-
Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5449:1, s. 359-366
-
Konferensbidrag (refereegranskat)abstract
- Radiative lifetimes of 11 levels in Cd I belonging to the 5s5p 1po1 and 5snd 3D1,2(n=6-9) and 5sns 3S1 (n=7,8) series, and of 5 levels of Cd II belonging to the 4d105p 2po1/2,3/2, 4d106s 2S1/2, and 4d105d 2D3/2,5/2 configurations were measured using the time-resolved laser-induced fluorescence technique. Free neutral and singly ionized cadmium were generated by laser ablation. Single- or two-step excitation processes were used to populate the levels under study. Transition probabilities and oscillator strengths for Cd I and Cd II transitions were also deduced by combining the experimental lifetimes and theoretical branching fractions obtained in multiconfigurational relativistic Hartree-Fock calculations, taking core-polarisation effects into account
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| 67. |
- Xu, Huailiang, et al.
(författare)
-
Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd II)
- 2003
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 346:2, s. 433-440
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd II in the energy range 20 500- 32 500 cm(-1). For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree-Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0-1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology.
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| 68. |
- Xu, Huailiang, et al.
(författare)
-
Time-resolved laser-induced fluorescence lifetime measurements and relativistic Hartree-Fock calculations of transition probabilities in SmII
- 2003
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:24, s. 4773-4787
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 47 levels of the astrophysically important ion Sm1+ over the energy range 21000-36 000 cm(-1). The new results have been compared with previous measurements but also with theoretical calculations taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for many levels of this complex ion. New calculated transition probabilities are deduced from the experimental lifetimes and from the theoretical branching fractions for 162 transitions of astrophysical interest. These results will help astrophysicists in the quantitative investigation of the chemical composition of CP stars.
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| 69. |
- 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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| 70. |
- Zhang, Z. G, et al.
(författare)
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Natural radiative lifetimes in Ce II
- 2001
-
Ingår i: Physica Scripta. Topical Issues. - 0281-1847. ; 63:2, s. 122-127
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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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| 71. |
- 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
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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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| 72. |
- Zhang, Zhiguo, et al.
(författare)
-
Radiative lifetime measurements and oscillator strengths of astrophysical interest in HoIII
- 2002
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 384:1, s. 364-370
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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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| 73. |
- Zhang, Zhiguo, et al.
(författare)
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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
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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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