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See detailRadiative decay data for highly excited Zr I levels
Malcheva, G.; Mayo, R.; Ortiz, M. et al

in Monthly Notices of the Royal Astronomical Society (2009), 395

Radiative lifetimes of 17 excited levels in Zr I, in the energy interval 29 000–40 974 cm−1, have been investigated using the time-resolved laser-induced fluorescence method. The levels belong to the ... [more ▼]

Radiative lifetimes of 17 excited levels in Zr I, in the energy interval 29 000–40 974 cm−1, have been investigated using the time-resolved laser-induced fluorescence method. The levels belong to the 4d25s5p, 4d35p and 4d5s25p electronic configurations and were excited in a single-step process from either the ground term, 4d25s2 a 3F, or from the low-lying 4d25s2 a 3P and a 5F terms. For three levels, we confirm previous measurements while for 14 of the levels the lifetimes have been measured for the first time. The experimental results are compared to theoretical calculations performed with a multiconfiguration relativistic Hartree–Fock method including core-polarization effects. Theoretical transition probabilities of astrophysical interest, scaled by the experimental lifetimes, for the depopulating channels of the investigated levels are also presented. [less ▲]

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See detailRadiative decay from the 7s(1/2) level in Pb+ and transition probabilities of astrophysical interest in Pb+ and Bi++
Quinet, Pascal ULg; Biémont, Emile ULg; Palmeri, P. et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2007), 40(10), 1705-1712

In the present work, we report on experimental and theoretical determination of the decay rates from the 7s(1)/2 state in singly ionized lead. Lifetime measurements performed using time-resolved laser ... [more ▼]

In the present work, we report on experimental and theoretical determination of the decay rates from the 7s(1)/2 state in singly ionized lead. Lifetime measurements performed using time-resolved laser-induced fluorescence spectroscopy and lifetime computations carried out with themulticonfiguration Dirac-Fock method allow us to solve the discrepancies previously observed between theory and experiment for this level. New transition probabilities are proposed for the two depopulation channels, i. e. the 6p(1/2-7s1/2) and 6p(3/2-7s1/2) transitions of astrophysical interest in Pb II and Bi III, respectively. [less ▲]

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See detailRadiative decay of the 4d(5)(S-6)5p z(5,7)P(o) states in TcII: comparison along the homologous and isoelectronic sequences. Application to astrophysics
Palmeri, P.; Quinet, Pascal ULg; Biémont, Emile ULg et al

in Monthly Notices of the Royal Astronomical Society (2007), 374(1), 63-71

Using three independent theoretical approaches (CA, HFR+CP, AUTOSTRUCTURE), oscillator strengths have been calculated for a set of Tc II transitions of astrophysical interest and the reliability of their ... [more ▼]

Using three independent theoretical approaches (CA, HFR+CP, AUTOSTRUCTURE), oscillator strengths have been calculated for a set of Tc II transitions of astrophysical interest and the reliability of their absolute scale has been assessed. The examination of the spectra emitted by some Ap stars has allowed the identification of Tc II transitions in HD 125248. This Tc II detection should however await confirmation from spectral synthesis relying on dedicated model atmospheres. New partition functions are also provided for Tc I, TcII and Tc III for temperatures ranging between 4000 and 13 000 K. [less ▲]

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See detailRadiative decay rates for W I, W II and W III allowed and forbidden transitions of interest for spectroscopic diagnostics in fusion plasmas
Quinet, Pascal ULg; Vinogradoff, V.; Palmeri, P. et al

in Journal of Physics : B Atomic Molecular & Optical Physics (2010), 43

Transition probabilities for allowed and forbidden lines in neutral, singly ionized and doubly ionized tungsten are discussed in the present paper. For the electric dipole transitions, recommended values ... [more ▼]

Transition probabilities for allowed and forbidden lines in neutral, singly ionized and doubly ionized tungsten are discussed in the present paper. For the electric dipole transitions, recommended values are proposed from a critical evaluation of the data available in the literature. For the magnetic dipole and electric quadrupole transitions, for which no data have been published so far, a new set of radiative rates has been obtained using a relativistic Hartree–Fock approach including core-polarization effects. The tables summarizing the compiled data are expected to be useful for plasma modelling in fusion reactors. [less ▲]

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See detailRadiative forces and pulsation in beta Cephei stars
Bourge, P*-O; Alecian, G.; Thoul, Anne ULg et al

in Communications in Asteroseismology (2006), 147

Recently radiatively-driven diffusion in beta Cephei stars has been suggested as a possible explanation to account for excitation of the observed oscillation modes of the beta Cephei stars nu Eridani and ... [more ▼]

Recently radiatively-driven diffusion in beta Cephei stars has been suggested as a possible explanation to account for excitation of the observed oscillation modes of the beta Cephei stars nu Eridani and 12 Lacertae. Preliminary results (Bourge and Alecian 2006) show that microscopic diffusion of iron could indeed occur in a region situated just above the opacity bump of the iron group elements. This diffusion has little influence on the position of the star in the HR diagram and on the spectrum of low radial order eigenfrequencies. It does, however, increase the number of excited frequencies. We show here that the ratio between the number of p-modes to the number of g-modes could be used as a signature of this diffusion process. [less ▲]

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See detailRadiative forces in expanding envelopes
Surdej, Jean ULg

in Astronomy and Astrophysics (1978), 62

The escape probability method introduced by Sobolev (1957) is applied to derive expressions for the radiative forces acting on atoms by the resonance scattering of radiation in envelopes which expand ... [more ▼]

The escape probability method introduced by Sobolev (1957) is applied to derive expressions for the radiative forces acting on atoms by the resonance scattering of radiation in envelopes which expand spherically with positive or negative radial-velocity gradients. In the latter case, it is shown that the contribution of the whole stellar envelope to the radiative force acting on individual atoms has the same effect as the one due to the stellar core radiation; i.e., a radial outward acceleration. Numerical applications to a two-level atom model illustrate the behavior of radiative forces in outward-accelerating and outward-decelerating stellar envelopes. [less ▲]

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See detailRadiative lifetime and oscillator strength determinations in potassium ions (K V, K VI and K VII)
Biémont, Emile ULg; Garnir, Henri-Pierre ULg; Lefèbvre, P.-H. et al

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2006), 40(1), 91-99

Oscillator strengths have been calculated for the transitions depopulating levels of the 3s(2)3p(3), 3s3p(4) configurations of K V, of the 3s(2)3p(2), 3s3p(3) configurations of K VI and of the 3s(2)3p ... [more ▼]

Oscillator strengths have been calculated for the transitions depopulating levels of the 3s(2)3p(3), 3s3p(4) configurations of K V, of the 3s(2)3p(2), 3s3p(3) configurations of K VI and of the 3s(2)3p, 3s3p(2), 3p(3) and 3s3p3d configurations of K VII. A multiconfiguration Dirac-Fock method, incorporating the relativistic two-body Breit interaction and quantum electrodynamics corrections due to self-energy and vacuum polarization, has been used for the calculations. The reliability of this approach has been tested by comparison with relativistic Hartree-Fock calculations and also with some experimental measurements performed by beam-foil spectroscopy at a beam energy of 1.7 MeV. [less ▲]

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See detailRadiative lifetime and oscillator strength determinations in SmIII
Biémont, Emile ULg; Garnir, Henri-Pierre ULg; Litzen, U. et al

in Astronomy and Astrophysics (2003), 399(1), 343-349

Radiative lifetimes of 6 levels belonging to the 4f(5)((6)Hdegrees, (6)Fdegrees)5d configuration of Sm III have been measured for the first time using a time-resolved laser-induced fluorescence technique ... [more ▼]

Radiative lifetimes of 6 levels belonging to the 4f(5)((6)Hdegrees, (6)Fdegrees)5d configuration of Sm III have been measured for the first time using a time-resolved laser-induced fluorescence technique. Experimental data have been compared with semi-empirical calculations. The agreement is excellent for 4 levels with (6)Fdegrees as a parent term. Larger discrepancies (53 and 37%) are observed for 2 levels with (6)Hdegrees and (6)Fdegrees, respectively, as a parent term and are explainable by strong mixing and cancellation effects occurring in the line strength calculations which are responsible of "instabilities" occurring in the lifetimes considered as a function of J value within the term. Branching ratios for the lines depopulating the levels of interest have been measured by Fourier transform spectroscopy. A first set of oscillator strengths has been deduced for this ion. [less ▲]

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See detailRadiative lifetime and oscillator strength determinations in XeVI
Biémont, Emile ULg; Buchard, V.; Garnir, Henri-Pierre ULg et al

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2005), 33(2), 181-191

Transition probabilities have been calculated for Δ n = 0 and Δ n = 1 transitions connecting the 5s(2) nl [np ( n = 5- 8); nf ( n = 4- 5); nh ( n = 6- 8); nk ( n = 8)], 5s5pnl ( nl = 5d, 6s), 5p(3) and 5s ... [more ▼]

Transition probabilities have been calculated for Δ n = 0 and Δ n = 1 transitions connecting the 5s(2) nl [np ( n = 5- 8); nf ( n = 4- 5); nh ( n = 6- 8); nk ( n = 8)], 5s5pnl ( nl = 5d, 6s), 5p(3) and 5s(2) nl [(ns (n = 6- 8); nd (n = 5- 8); ng ( n = 5- 6); ni ( n = 7- 8)] and 5s5p(2) configurations of Xe VI. Core-polarization effects have been included in the framework of a Hartree-Fock approach. The accuracy of the present set of results has been assessed through comparisons with radiative lifetime measurements. Good agreement has been observed between theory and experiment. [less ▲]

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See detailRadiative lifetime and transition probabilities in CdI and CdII
Xu, H. L.; Persson, A.; Svanberg, S. et al

in Physical Review A (2004), 70(4), 1-14

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 ... [more ▼]

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. [less ▲]

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See detailRadiative lifetime measurements and calculations in doubly ionized tantalum (Ta III)
Fivet, V.; Biémont, Emile ULg; Engström, L. 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 ▲]

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See detailRadiative lifetime measurements and calculations of odd-parity highly excited levels in Ba I
Zhang, W; Palmeri, P; Quinet, Pascal ULg et al

in Physical Review. A (2010), 82

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See detailRadiative lifetime measurements and oscillator strength determination for transitions in singly ionized praseodymium (Pr II)
Biémont, Emile ULg; Lefèbvre, P.-H.; Quinet, Pascal ULg et al

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2003), 27(1), 33-41

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 ... [more ▼]

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. [less ▲]

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See detailRadiative lifetime measurements and oscillator strengths of astrophysical interest in HoIII
Zhang, Z. G.; Somesfalean, G.; Svanberg, S. et al

in Astronomy and Astrophysics (2002), 384(1), 364-370

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 ... [more ▼]

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|r|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. [less ▲]

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See detailRadiative lifetime measurements and semi-empirical transition probability calculations in neutral rhenium
Palmeri, P.; Quinet, Pascal ULg; Biémont, Emile ULg et al

in Physica Scripta (2006), 74(3), 297-303

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 ... [more ▼]

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. [less ▲]

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See detailRadiative lifetime measurements and transition probabilities of astrophysical interest in Er III
Biémont, Emile ULg; Garnir, Henri-Pierre ULg; Bastin, Thierry ULg et al

in Monthly Notices of the Royal Astronomical Society (2001), 321

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 ... [more ▼]

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. [less ▲]

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See detailRadiative lifetime measurements and transition probability calculations in lanthanide ions
Quinet, Pascal ULg; Palmeri, P.; Biémont, Emile ULg et al

in Journal of Alloys and Compounds (2002), 344(1-2), 255-259

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 ... [more ▼]

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. [less ▲]

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See detailRadiative Lifetime Measurements in Dy II and the Solar Abundance of Dysprosium
Biémont, Emile ULg; Löwe, R. M.

in Astronomy and Astrophysics (1993), 273

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See detailRadiative lifetime measurements in ErII by time-resolved laser spectroscopy
Xu, H. L.; Jiang, Z. K.; Zhang, Z. G. et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2003), 36(9), 1771-1781

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 ... [more ▼]

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. [less ▲]

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See detailRadiative lifetime measurements in Tm III with time-resolved laser spectroscopy and comparisons with HFR calculations
Li, Z. S.; Zhang, Z. G.; Lokhnygin, V. et al

in Journal of Physics : B Atomic Molecular & Optical Physics (2001), 34

Natural radiative lifetimes of eight levels in Tm III were measured with the time-resolved laser-induced fluorescence (LIF) technique. Free doubly ionized thulium ions were obtained in a laser-produced ... [more ▼]

Natural radiative lifetimes of eight levels in Tm III 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 4f126p levels while larger discrepancies are noted for some 4f125d levels. [less ▲]

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