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1.
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2.
  • Berzinsh, U, et al. (author)
  • Radiative lifetimes for the 4p excited states of phosphorus and the oscillator strengths of solar lines
  • 1997
  • In: Astronomy & Astrophysics. - 0004-6361. ; 326:1, s. 412-416
  • Journal article (peer-reviewed)abstract
    • Radiative lifetimes for the levels of the 3s(2)3p(2)4p configuration in neutral phosphorus have been determined experimentally for the first time and also theoretically. Experiments were performed by using two-photon UV laser excitation and subsequent fluorescence detection in a laser-produced plasma. In relativistic Hartree-Fock calculations, the Cowan code extended to 42 configurations was used. Finally, the lifetimes for all the 13 excited states in the 4p configuration were calculated and for 6 of them the values were measured experimentally. Theoretical branching ratios were combined with experimental lifetimes, to deduce oscillator strengths and these were used for the evaluation of the phosphorus abundance in the sun. A value of 5.49 (0.04) was obtained in the usual logarithmic scale.
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3.
  • Biemont, E, et al. (author)
  • Core-polarization effects and radiative lifetime measurements in PrIII
  • 2001
  • In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 64:2
  • Journal article (peer-reviewed)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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4.
  • Biémont, E, et al. (author)
  • Decay of metastable states in Nd II
  • 2007
  • In: The European physical journal D Atomic, molecular and optical physics. ; 41, s. 211-
  • Journal article (peer-reviewed)
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5.
  • Biémont, É., et al. (author)
  • Decay of metastable states in NdII
  • 2007
  • In: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 41:2, s. 211-219
  • Journal article (peer-reviewed)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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6.
  • Biemont, E, et al. (author)
  • Doubly ionized thorium: Laser lifetime measurements and transition probability determination of interest in cosmochronology
  • 2002
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 567:2, s. 1276-1283
  • Journal article (peer-reviewed)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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7.
  • Biemont, E, et al. (author)
  • Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII
  • 2001
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:10, s. 1869-1876
  • Journal article (peer-reviewed)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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8.
  • Biemont, E, et al. (author)
  • Experimental lifetime determination in neutral praseodymium (Pr I) and neodymium (Nd I)
  • 2004
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:7, s. 1381-1389
  • Journal article (peer-reviewed)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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9.
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10.
  • Biemont, E, et al. (author)
  • Importance of an M2 depopulating channel for a KrII metastable state
  • 2004
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:6, s. 063003-
  • Journal article (peer-reviewed)abstract
    • An experimental investigation of the radiative lifetime of the metastable 4s(2)4p(4)(P-3)4d D-4(7/2) level in Kr II shows an unusual situation regarding the importance of an M2 depopulation channel. While the first order M1 and E2 channels are expected to contribute in a dominant way to the decay, the experimental result, obtained using a laser probing technique on a stored ion beam, tau=0.57+/-0.03 s, is far too short to be due to these channels according to our relativistic multiconfiguration Dirac-Fock calculation. Only if second order contributions to the decay branches (including essentially the M2 contribution) are taken into account in the calculations could the unexpected short lifetime be explained.
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11.
  • Biemont, E, et al. (author)
  • Lifetime measurements and calculations in LaI
  • 2004
  • In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 30:2, s. 157-162
  • Journal article (peer-reviewed)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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12.
  • Biemont, E, et al. (author)
  • Lifetime measurements and calculations in singly ionized ytterbium
  • 2002
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 35:22, s. 4743-4749
  • Journal article (peer-reviewed)abstract
    • New radiative lifetimes, measured by time-resolved laser-induced fluorescence spectroscopy, are reported for five Rydberg states of singly ionized ytterbium. Free Yb+ ions were produced in a laser-induced plasma. The experimental results have been compared with HFR calculations, taking core-polarization effects into account, and a good agreement (within 25%) between theory and experiment is observed for four levels. HFR results are also proposed for np (n less than or equal to 7) and nf (n less than or equal to 8) Rydberg states and compared with available data.
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13.
  • Biemont, E., et al. (author)
  • Lifetime measurements and calculations in Y+ and Y2+ ions
  • 2011
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 414:4, s. 3350-3359
  • Journal article (peer-reviewed)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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14.
  • Biemont, E, et al. (author)
  • Lifetime measurements for doubly ionized uranium
  • 2002
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:7, s. 1701-1705
  • Journal article (peer-reviewed)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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15.
  • Biemont, E, et al. (author)
  • Lifetimes along perturbed Rydberg series in neutral thallium
  • 2005
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:19, s. 3547-3558
  • Journal article (peer-reviewed)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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16.
  • Biemont, E, et al. (author)
  • Lifetimes and oscillator strengths for ultraviolet transitions in neutral sulfur
  • 1998
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 502:2, s. 1010-1014
  • Journal article (peer-reviewed)abstract
    • A consistent set of f-values for vacuum ultraviolet lines of S I is deduced from a combination of laser lifetime measurements and theoretical branching ratios. The new results are compared with results deduced from absorption by interstellar gas toward zeta Ophiuchi, and good agreement is observed for most transitions.
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17.
  • Biemont, E, et al. (author)
  • Measurement of radiative lifetimes and determination of transition probabilities of astrophysical interest in HoIII
  • 2001
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 328:4, s. 1085-1090
  • Journal article (peer-reviewed)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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18.
  • Biemont, E, et al. (author)
  • New f-values in neutral lead obtained by time-resolved laser spectroscopy, and astrophysical applications
  • 2000
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 312:1, s. 116-122
  • Journal article (peer-reviewed)abstract
    • Natural radiative lifetimes have been measured for three odd-parity levels of neutral lead using time-resolved UV laser-induced fluorescence from a laser-produced plasma. These new lifetimes, as well as additional recent values obtained by laser spectroscopy, combined with theoretical branching ratios deduced from a relativistic Hartree-Fock calculation taking core polarization effects into account, have allowed the deduction of a new set of accurate f-values of astrophysical interest. Using the new lifetime value for 6p7s (1/2, 1/2)(0)degrees, a refined value of the lead abundance in the solar photosphere is deduced: A(Pb) = 2.00 +/- 0.06 on the usual logarithmic scale, allowing the resolution of the long-standing discrepancy previously observed between the solar photosphere and meteorites.
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19.
  • Biémont, E, et al. (author)
  • Radiative lifetime and oscillator strength determinations in Sm III
  • 2003
  • In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 399:1, s. 343-349
  • Journal article (peer-reviewed)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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20.
  • Biemont, E, et al. (author)
  • Radiative lifetime measurements and oscillator strength determination for transitions in singly ionized praseodymium (Pr II)
  • 2003
  • In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 27:1, s. 33-41
  • Journal article (peer-reviewed)abstract
    • New radiative lifetimes for 20 levels of Pr II have been measured using the time-resolved laser-induced fluorescence (LIF) technique. The combination of these experimental values with theoretical branching fractions (BF) obtained with the pseudo-relativistic Hartree-Fock (HFR) approach has allowed us to determine oscillator strengths and transition probabilities for about 150 lines appearing in the spectral region between 369.9 and 741.2 nm. A detailed discussion of our new results and comparisons with previous data are also given in the present paper.
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21.
  • Biemont, E, et al. (author)
  • Radiative lifetime measurements and transition probabilities of astrophysical interest in ErIII
  • 2001
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 321:3, s. 481-486
  • Journal article (peer-reviewed)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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22.
  • Biemont, E, et al. (author)
  • Radiative lifetimes, branching fractions and transition probabilities in Ge I - solar implications
  • 1999
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 303:4, s. 721-726
  • Journal article (peer-reviewed)abstract
    • New radiative lifetimes have been measured for the 5s (3)P(0,1,2)degrees and 5s (1)P(1)degrees levels of Ge I using a laser-produced plasma subject to selective laser excitation. A diffraction grating based emission spectrometer of moderately high resolution has been used to remeasure the branching ratios of the 4p-5s depopulating transitions. The oscillator strengths of astrophysical interest, which have been derived from these new data, are compared with theoretical values calculated within a pseudo-relativistic Hartree-Fock approach. The new set of f-values has been compared with the few results available in the literature, which are generally characterized by a large scatter and a low accuracy. The solar photospheric abundance of germanium deduced from the new atomic data of the present work is A(Ge) = 3.58 +/- 0.05, on the usual logarithmic scale, in agreement with the meteoritic value.
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23.
  • Biemont, E, et al. (author)
  • Time-resolved laser-induced fluorescence lifetime measurements and theoretical transition probabilities in Tb III
  • 2002
  • In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 65:5
  • Journal article (peer-reviewed)abstract
    • Lifetimes of four short-lived levels belonging to the 4f(8)(F-7)6p configuration of Tb III have been measured using a two-step excitation time-resolved laser-induced fluorescence technique. They agree quite well with multiconfigurational relativistic Hartree-Fock calculations performed with inclusion of core-polarization effects. Using the experimental lifetimes and the theoretical branching fractions, a set of transition probabilities has been deduced for this ion.
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24.
  • Blagoev, K, et al. (author)
  • Radiative lifetimes of 6sns S-3(1) and 6snd D-3(1) excited states of HgI
  • 2002
  • In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 66:3
  • Journal article (peer-reviewed)abstract
    • Natural radiative lifetimes have been measured along the 6sns S-3(1) (n=7-10) and 6snd D-3(1) (n=6-11) Rydberg series of neutral mercury using time-resolved laser-induced fluorescence spectroscopy in a laser-produced mercury plasma. The states of Hg I investigated in the present work were populated from the ground state by a stepwise excitation process. Relativistic Hartree-Fock calculations, including intravalence interactions and core-polarization effects, have been performed and the theoretical lifetimes have been compared with the measurements.
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25.
  • Blagoev, KB, et al. (author)
  • Radiative lifetimes of Zn I, II excited states
  • 2004
  • In: Physica Scripta. - 0031-8949. ; 69:6, s. 433-440
  • Journal article (peer-reviewed)abstract
    • Radiative lifetimes of excited states of Zn I (3d(10)4sns S-3(1), n = 6-8; 3d(10) 4snd D-3, n = 4-7) and Zn II (3d(10) 4p P-2(1/2.3/2), 4d D-2(3/2,5/2), 3d(10)5S S-2(1/2)) have been measured using a time-resolved laser-induced fluorescence technique. Single- or two-step excitation of atoms and ions produced by laser ablation was employed. The experimental radiative lifetimes have been compared with theoretical results obtained within a multiconfigurational relativistic Hartree-Fock approach taking core-polarization effects into account.
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26.
  • Dai, Zhenwen, et al. (author)
  • Time-resolved laser-induced fluorescence measurements of Rydberg states in LuI and comparison with theory
  • 2003
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 36:3, s. 479-487
  • Journal article (peer-reviewed)abstract
    • Time-resolved laser-induced fluorescence measurements have been performed for ten odd Rydberg states of neutral lutetium, belonging to the 6s(2)(S-1)np(n = 8-9) and 6 s(2)(S-1)nf (n = 5-8) series. For 6S(2)(S-1)8p and 6s(2)(S-1)7f, the experimental lifetimes corresponding to the two J values within the doublet differ substantially. Comparison with theoretical values, calculated with extensive configuration interaction and core-polarization effects included, shows that the experimental trends are adequately reproduced both for np (n = 8-9) and nf (n = 5-8) states.
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27.
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28.
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29.
  • Fivet, V, et al. (author)
  • Radiative lifetimes and transition probabilities in TaI
  • 2006
  • In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 37:1, s. 29-35
  • Journal article (peer-reviewed)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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30.
  • Fivet, V., et al. (author)
  • Transition probabilities and lifetimes for atoms and ions from the sixth row of the periodic table and the database DESIRE
  • 2007
  • In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 156, s. 250-254
  • Journal article (peer-reviewed)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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31.
  • Fivet, V., et al. (author)
  • Transition probabilities and lifetimes in gold (Au I and Au II)
  • 2006
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:17, s. 3587-3598
  • Journal article (peer-reviewed)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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32.
  • Gurell, Jonas, 1981-, et al. (author)
  • Laser-probing measurements and calculations of lifetimes of the 5d 2D3/2 and 5d 2D5/2 metastable levels in Ba II
  • 2007
  • In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
  • Journal article (peer-reviewed)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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33.
  • Gurell, J., et al. (author)
  • 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
  • In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
  • Journal article (peer-reviewed)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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34.
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35.
  • Li, Z. S, et al. (author)
  • Determination of radiative lifetimes of neutral sulphur by time-resolved three-photon VUV laser spectroscopy
  • 1998
  • In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 2:1, s. 11-14
  • Journal article (peer-reviewed)abstract
    • Radiative lifetimes of the highly exited states 3p(3)8s S-3(1)0 and 3p(3)6d D-3(1,2,3)0 of neutral sulphur have been measured using time-resolved laser-induced fluorescence. The sulphur atoms were generated in a laser-produced plasma. The investigated states were populated through a two-step process involving a two-photon excitation to the lowest excited tripler state of even parity 3p(4) P-3(0,1,2), followed by a one-photon excitation to the investigated state. We obtained tau(8s(3)S(1)(0)) = 40 +/- 5 ns and tau(6d(3)D(1,2,3)(0)) = 75 +/- 7 ns. These values are much longer than theoretically predicted ones and much shorter than those indirectely inferred from astronomical data.
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36.
  • Li, Z. S, et al. (author)
  • Lifetime measurements in odd-parity Rydberg series of neutral lead by time-resolved laser spectroscopy
  • 1998
  • In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 57:5, s. 3443-3449
  • Journal article (peer-reviewed)abstract
    • Natural radiative lifetimes have been measured in the odd-parity Rydberg series 6pns (n=7-13) and 6pnd (n=6-13) of neutral lead using time-resolved UV laser-induced fluorescence from a laser-produced plasma. A relativistic Hartree-Fock calculation taking configuration interaction into account in a detailed way has also been performed for odd-as well as even-parity states for testing the ability of this approach to correctly predict radiative properties of heavy atoms. A generally good overall agreement between experimental and theoretical lifetimes has been achieved except for a few levels.
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37.
  • Li, Z. S, et al. (author)
  • Lifetime measurements in Yb II with time-resolved laser spectroscopy
  • 1999
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 32:7, s. 1731-1737
  • Journal article (peer-reviewed)abstract
    • Natural radiative lifetimes of 10 levels of singly ionized ytterbium have been measured with time-resolved laser spectroscopy. Free Yb+ ions were produced in a laser-induced plasma. A stimulated Brillouin scattering technique has been used to produce laser pulses as short as 1 ns for the excitation of short-lived Yb+ states. Pseudo-relativistic Hartree-Fock calculations, taking into account the core-polarization effects, have also been performed. A good agreement of the measured and the calculated lifetime values has been achieved.
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38.
  • Li, Z. S, et al. (author)
  • Radiative lifetime measurements in TmIII with time-resolved laser spectroscopy and comparisons with HFR calculations
  • 2001
  • In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:8, s. 1349-1359
  • Journal article (peer-reviewed)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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39.
  • Li, Z. S, et al. (author)
  • Radiative properties of neutral germanium obtained from excited-state lifetime and branching-ratio measurements and comparison with theoretical calculations
  • 1999
  • In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:1, s. 198-208
  • Journal article (peer-reviewed)abstract
    • Using time-resolved UV laser-induced fluorescence from a laser-produced plasma, natural radiative lifetimes have been measured for 21 levels of Ge I belonging to the odd-parity 4p4d, 4p5d, and 4p6s configurations. Stimulated Brillouin scattering in water has allowed us to compress Nd:YAG laser pulses pumping a dye laser (where YAG denotes yttrium aluminum garnet), thus yielding 1-ns tunable laser pulses to enable accurate measurements of short lifetimes. Branching ratios of Ge I have been measured by inductively coupled plasma emission spectrometry, the intensity calibration being performed by means of Ar lines emitted by a hollow-cathode lamp. The experimental lifetimes and branching ratios have been combined in order to provide a set of accurate transition probabilities for the 4p-5s and 4p-4d transitions. A relativistic Hartree-Fock; calculation, taking configuration-interaction and polarization effects into account, has been combined with a least-squares optimization procedure of the Slater and spin-orbit integrals in order to test the ability of this approach to correctly predict radiative properties of the group-IV elements. Good agreement between experimental and theoretical transition probability values has been achieved for most of the transitions considered.
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40.
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41.
  • Lundin, P., et al. (author)
  • Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar
  • 2007
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99, s. 213001-
  • Journal article (peer-reviewed)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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42.
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43.
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44.
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45.
  • Malcheva, G, et al. (author)
  • Radiative lifetimes and transition probabilities of astrophysical interest in ZrII
  • 2006
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 367:2, s. 754-762
  • Journal article (peer-reviewed)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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46.
  • Malcheva, G., et al. (author)
  • Radiative parameters of Nb i excited states
  • 2011
  • In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 412:3, s. 1823-1827
  • Journal article (peer-reviewed)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.
  •  
47.
  • Nilsson, Hampus, et al. (author)
  • Lifetime measurements and transition probability calculations in singly ionized tungsten (W II)
  • 2008
  • In: 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
  • Journal article (peer-reviewed)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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48.
  • Nilsson, Hampus, et al. (author)
  • Transition probabilities of astrophysical interest in the niobium ions Nb+ and Nb2
  • 2010
  • In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511
  • Journal article (peer-reviewed)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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49.
  • Palmeri, P., et al. (author)
  • Lifetime measurements and calculated transition probabilities in W III
  • 2008
  • In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 78:1
  • Journal article (peer-reviewed)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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50.
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