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Atomic data and spectral model for Fe II ; ; et al in Astrophysical Journal (in press) Detailed reference viewed: 26 (1 ULg)Uncertainties in atomic data and propagation of uncertainties through spectral models ; ; Quinet, Pascal et al in Astrophysical Journal (2013), 770 Detailed reference viewed: 7 (1 ULg)Transition probabilities of astrophysican interest in the niobium ions (Nb II and Nb III) ; ; et al in Astronomy and Astrophysics (2010) 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 ... [more ▼] 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 4d35p configuration in the wavelength region 2240−4700 Å. For the first time, we present theoretical transition probabilities of 76 Nb III transitions with wavelengths in the range 1430−3140 Å. The derived solar photospheric niobium abundance log = 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. [less ▲] Detailed reference viewed: 58 (2 ULg)Atomic structure calculations and Beam-foil observations of La IV Biémont, Emile ; ; et al in Canadian Journal of Physics (2009), 87 Relativistic Hartree–Fock and multiconfigurational Dirac–Fock calculations of atomic structure and transition rates have been carried out in trebly ionized lanthanum (La3+, Z = 57). The calculations have ... [more ▼] Relativistic Hartree–Fock and multiconfigurational Dirac–Fock calculations of atomic structure and transition rates have been carried out in trebly ionized lanthanum (La3+, Z = 57). The calculations have to cope with configuration interaction effects but also with the very complex situation of the collapse of the 4f wave function. The calculations are compared to experimental data obtained with beam-foil spectroscopy in the extreme ultraviolet, at ion energies that favour <br />the production of the spectrum La IV. Besides lines known from sliding spark discharges, many more lines are observed that have not yet been identified. Time-resolved measurements yield three level lifetimes in La IV that agree roughly with the results of our own calculations. [less ▲] Detailed reference viewed: 41 (5 ULg)Branching fractions and A values in singly ionized tantalum (Ta II) Quinet, Pascal ; ; et al in Astronomy and Astrophysics (2009), 493 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 31 (0 ULg)Experimental and theoretical radiative decay rates for highly excited ruthenium atomic levels and the solar abundance of ruthenium ; Quinet, Pascal ; et al in Monthly Notices of the Royal Astronomical Society (2009), 396 The solar photospheric abundance of ruthenium is revised on the basis of a new set of oscillator strengths derived for Ru I transitions with wavelengths in the spectral range 2250–4710 Å. The new ... [more ▼] The solar photospheric abundance of ruthenium is revised on the basis of a new set of oscillator strengths derived for Ru I transitions with wavelengths in the spectral range 2250–4710 Å. The new abundance value (in the usual logarithmic scale where the solar hydrogen abundance is equal to 12.00), ARu = 1.72 ± 0.10, is in agreement with the most recent meteoritic result, ARu = 1.76 ± 0.03. The accuracy of the transition probabilities, obtained using a relativistic Hartree–Fock model including core-polarization effects, has been assessed by comparing the theoretical lifetimes with previous experimental results. A comparison is also made with new measurements performed in this work by the time-resolved laser-induced fluorescence spectroscopy for 10 highly excited odd-parity levels of Ru I [less ▲] Detailed reference viewed: 12 (0 ULg)Lifetime measurements in Ru II and calculated oscillator strengths in Ru II and Ru III ; Quinet, Pascal ; et al in Journal of Physics : B Atomic Molecular & Optical Physics (2009), 42 A new set of theoretical f -values is reported for 178 Ru II transitions of astrophysical interest, involving energy levels below 58 000 cm−1. The theoretical model, including core-polarization effects ... [more ▼] A new set of theoretical f -values is reported for 178 Ru II transitions of astrophysical interest, involving energy levels below 58 000 cm−1. The theoretical model, including core-polarization effects, has been tested by comparing theoretical lifetimes with new measurements performed by time-resolved laser-induced fluorescence spectroscopy for 23 4d6(5D)5p odd levels of Ru II and by comparing theoretical and experimental Land´e g-factors. The first set of transition probabilities is proposed for 25 strong lines depopulating the 4d55p 5,7P◦ terms of Ru III. The new results will allow quantitative investigations of stellar spectra and allow the astrophysicists to refine the ruthenium abundance in stars. [less ▲] Detailed reference viewed: 13 (1 ULg)Lifetime measurements and calculated transition probabilities in WIII ; Quinet, Pascal ; et al in Physica Scripta (2008), 78 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 ... [more ▼] 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 < 70 000 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. [less ▲] Detailed reference viewed: 15 (0 ULg)Lifetime measurements and transition probability calculations in singly ionized tungsten (WII) ; ; et al in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2008), 49 New measurements of radiative lifetimes for 9 levels in singly ionized tungsten (Wii) have been performed with the time-resolved laser-induced-fluorescence technique. Transition probabilities have been ... [more ▼] New measurements of radiative lifetimes for 9 levels in singly ionized tungsten (Wii) 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. [less ▲] Detailed reference viewed: 18 (0 ULg)Radiative lifetime measurements and calculations in doubly ionized tantalum (Ta III) ; Biémont, Emile ; et al in Journal of Physics : B Atomic Molecular & Optical Physics (2008), 41 Radiative lifetimes of six odd-parity levels belonging to the 5d26p configuration of doubly ionized tantalum (Ta III) have been measured using the time-resolved-laser-inducedfluorescence technique ... [more ▼] Radiative lifetimes of six odd-parity levels belonging to the 5d26p configuration of doubly ionized tantalum (Ta III) have been measured using the time-resolved-laser-inducedfluorescence technique. Supporting theoretical calculations, including core-polarization effects, have been performed to model configuration interaction and to estimate branching fractions. The excellent agreement between the theoretical and experimental lifetimes allows us to assess the reliability of the 206 calculated transition probabilities. It is expected that this new set of results will be useful to astrophysicists for the investigation of the chemical composition of stars. [less ▲] Detailed reference viewed: 31 (1 ULg)Laser-induced-fluorescence lifetime measurements and relativistic Hartree-Fock oscillator strength calculations in singly ionized platinum Quinet, Pascal ; ; et al in Physical Review. A (2008), 77 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 44 (1 ULg)ATOMIC STRUCTURES OF HEAVY ELEMENTS : RECENT PROGRESS AND PERSPECTIVES Biémont, Emile ; ; et al Conference (2008) In the present paper, we discuss some recent advances concerning the determination of new radiative parameters (transition probabilities, oscillator strengths, radiative lifetimes, branching fractions ... [more ▼] In the present paper, we discuss some recent advances concerning the determination of new radiative parameters (transition probabilities, oscillator strengths, radiative lifetimes, branching fractions, Landé factors) in heavy ions. We also emphasize the difficulties that are frequently met in the field and that sometimes prevent obtaining accurate atomic data for the transitions of astrophysical interest. We concentrate particularly on the determination of radiative parameters for selected rare-earth (RE) ions (lanthanides and actinides) and for some atoms and ions of the sixth row of the periodic table. [less ▲] Detailed reference viewed: 13 (2 ULg)Experimental and theoretical transition probabilities in singly ionized gold Biémont, Emile ; ; et al in Monthly Notices of the Royal Astronomical Society (2007), 380(4), 1581-1588 Absolute transition probabilities have been measured for lines originating from the 5d(9)6d and 5d(9)7s electronic configurations in the spectrum of singly ionized gold (Au II). The laser-induced ... [more ▼] Absolute transition probabilities have been measured for lines originating from the 5d(9)6d and 5d(9)7s electronic configurations in the spectrum of singly ionized gold (Au II). The laser-induced breakdown spectroscopy has been applied to free gold atoms and ions produced by laser ablation. Absolute transition probabilities have been determined using the branching fraction and the Boltzmann plot methods. Theoretical branching fractions as well as radiative lifetime values have also been obtained by a relativistic Hartree-Fock method taking core polarization and configuration interaction effects into account. The new results are compared with previous results when available. [less ▲] Detailed reference viewed: 16 (0 ULg)Atomic data for radioactive elements RaI, RaII, AcI and AcII and application to their detection in HD 101065 and HR 465 Quinet, Pascal ; ; et al in Astronomy and Astrophysics (2007), 474(1), 307-314 Radiative data for transitions of astrophysical interest in radioactive elements Ra I, Ra II, Ac I and Ac II have been computed using a semi- empirical relativistic Hartree- Fock approach including core ... [more ▼] Radiative data for transitions of astrophysical interest in radioactive elements Ra I, Ra II, Ac I and Ac II have been computed using a semi- empirical relativistic Hartree- Fock approach including core polarization effects. Most of the oscillator strengths reported in the present paper are new. A possible detection of radium ( Ra II) and actinium ( Ac II) in the spectrum of the stars HD 101065 and HR 465 is examined and discussed. [less ▲] Detailed reference viewed: 20 (0 ULg)Transition probabilities in singly ionized promethium and the identification of PmII lines in Przybylski's star and HR 465 ; Quinet, Pascal ; Biémont, Emile et al in Monthly Notices of the Royal Astronomical Society (2007), 380(2), 771-780 The first theoretical transition probabilities are obtained for a set of 46 Pm ii transitions of astrophysical interest. These data fill in a gap in astrophysics and will allow to establish, on a firmer ... [more ▼] The first theoretical transition probabilities are obtained for a set of 46 Pm ii transitions of astrophysical interest. These data fill in a gap in astrophysics and will allow to establish, on a firmer basis, the presence of some lines of this radioactive element in the spectra of chemically peculiar stars and, consequently, a quantitative investigation of the stellar Pm abundance. A search for Pm ii lines in Przybylski's star (HD 101065) and in HR 465 is reported and discussed, supporting the detection of this ion. A more detailed quantitative analysis is awaiting the availability of dedicated model atmospheres for these stars. [less ▲] Detailed reference viewed: 18 (0 ULg)Lifetime and transition probability determination in xenon ions - The cases of XeVII and XeVIII Biémont, Emile ; Clar, Mathieu ; et al in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2007), 44(1), 23-33 Radiative lifetimes have been calculated for 15 levels of Xe VII belonging to the configurations 5s5p, 5p(2), 5s5d, 5s6s, 5p5d, 4f5p, 5p5d and 5s5f and for 4 levels of the 5p and 5d configurations of Xe ... [more ▼] Radiative lifetimes have been calculated for 15 levels of Xe VII belonging to the configurations 5s5p, 5p(2), 5s5d, 5s6s, 5p5d, 4f5p, 5p5d and 5s5f and for 4 levels of the 5p and 5d configurations of Xe VIII. A relativistic Hartree-Fock approach including core-polarization effects, on the one hand, and a purely relativistic multiconfiguration Dirac-Fock method, on the other hand, have been used for the calculations. The accuracy of the present set of results has been assessed through comparisons with radiative lifetime measurements obtained by beam-foil spectroscopy. A good agreement between theory and experiment is observed for most of the levels. A new set of transition probabilities is proposed for 169 transitions of Xe VII and 45 transitions of Xe VIII. [less ▲] Detailed reference viewed: 28 (0 ULg)Transition probabilities in complex ions: The case of americium ; Quinet, Pascal ; Biémont, Emile in Journal of Electron Spectroscopy and Related Phenomena (2007), 156 We report on the first calculations of transition probabilities in neutral americium, a heavy radioactive element belonging to the actinide group. A relativistic Hartree-Fock approach, including core ... [more ▼] We report on the first calculations of transition probabilities in neutral americium, a heavy radioactive element belonging to the actinide group. A relativistic Hartree-Fock approach, including core-polarization effects, has been used for obtaining branching fractions and radiative lifetimes for some low-lying levels belonging to the 7s7p configuration. A comparison with the few experimental results available shows reasonable agreement between theory and experiment. (c) 2006 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 12 (0 ULg)Transition probabilities and lifetimes for atoms and ions from the sixth row of the periodic table and the database DESIRE ; Quinet, Pascal ; et al in Journal of Electron Spectroscopy and Related Phenomena (2007), 156 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 22 (1 ULg)Laser-probing measurements and calculations of lifetimes of the 5d D-2(3/2) and 5d D-2(5/2) metastable levels in BaII ; Biémont, Emile ; et al in Physical Review A (2007), 75(5), 1-6 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 17 (0 ULg)Application of Laser Induced Breakdown Spectroscopy (LIBS) to the determination of transition probabilities of laser lines in Au II spectrum ; ; Biémont, Emile et al Conference (2007) Experimental branching fractions for laser lines arising from excited states of 5d97s configuration of Au II have been determined by application of Laser Induced Breakdown Spectroscopy (LIBS). The ... [more ▼] Experimental branching fractions for laser lines arising from excited states of 5d97s configuration of Au II have been determined by application of Laser Induced Breakdown Spectroscopy (LIBS). The experimental relative transition probabilities were converted into an absolute scale using theoretical values for the radiative lifetimes of the corresponding states, calculated in this work. Transition probabilities and radiative lifetimes have been determined by a relativistic Hartree - Fock method taking configuration interaction and core-polarization effects into account. A comparison of the present results with the available theoretical values has been made and shows a reasonable agreement although discrepancies are observed between theory and experiment for some transitions. [less ▲] Detailed reference viewed: 38 (0 ULg) |
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