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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 detailThe spectrum of the roAp star HD 101065 (Przybylski's star) in the Li I 6708 A spectral region
Shavrina, A V; Polosukhina, N S; Pavlenko, Ya V et al

in Astronomy and Astrophysics (2003), 409

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See detailRecent advances in the study of lanthanide atoms and ions
Biémont, Emile ULg; Quinet, Pascal ULg

in Physica Scripta (2003), T105

We present an overview of the recent developments concerning the spectroscopic properties of lanthanide atoms and ions (Z = 57-71). This review is focussed on the advances made during the past twenty ... [more ▼]

We present an overview of the recent developments concerning the spectroscopic properties of lanthanide atoms and ions (Z = 57-71). This review is focussed on the advances made during the past twenty years regarding the analysis of the spectra, the transition probabilities, the radiative lifetimes and also the hyperfine structures and isotope shifts. Theoretical aspects as well as experimental measurements are both covered in this paper including bibliographical references up to the end of 2001. Some astrophysical implications of the new atomic data concerning the chemical composition of the sun are briefly reviewed. Emphasis is also put on the new database D.R.E.A.M. developed on a web site of Mons University in Belgium. [less ▲]

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See detailX-Ray spectromicroscopy of clusters heated by fs laser radiation
Faenov, A.Ya.; Magunov, A. I.; Pikuz, T. A. et al

Conference (2003)

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See detailLifetime measurements and calculations in singly ionized ytterbium
Biémont, Emile ULg; Quinet, Pascal ULg; Dai, Z. W. et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2002), 35(22), 4743-4749

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 ... [more ▼]

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. [less ▲]

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See detailCore-polarization effects in doubly ionized cerium (Ce III) for transitions of astrophysical interest
Biémont, Emile ULg; Quinet, Pascal ULg; Ryabchikova, T. A.

in Monthly Notices of the Royal Astronomical Society (2002), 336(4), 1155-1160

The importance of core-polarization effects on oscillator strength determination in Ce III is emphasized. The inclusion of these effects in relativistic Hartree-Fock (HFR) calculations leads to ... [more ▼]

The importance of core-polarization effects on oscillator strength determination in Ce III is emphasized. The inclusion of these effects in relativistic Hartree-Fock (HFR) calculations leads to theoretical lifetime values for some 4f6p levels of this ion in close agreement with recent time-resolved laser-induced fluorescence measurements. These new atomic data, the most accurate to date, have allowed the refinement of the stellar abundance determination of cerium in the chemically peculiar star HD 192913, but have not altered in a drastic way the conclusions derived in recent analyses regarding the overabundance of this element. [less ▲]

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See detailCerium: The lithium substitute in post-AGB stars
Reyniers, M.; Winckel, H. V.; Biémont, Emile ULg et al

in Astronomy and Astrophysics (2002), 395(2), 35-38

In this letter we present an alternative identification for the line detected in the spectra of s-process enriched low-mass post-AGB stars around 6708 Angstrom and which was interpreted in the literature ... [more ▼]

In this letter we present an alternative identification for the line detected in the spectra of s-process enriched low-mass post-AGB stars around 6708 Angstrom and which was interpreted in the literature as due to Li. Newly released line lists of lanthanide species reveal, however, the likely identification of the line to be due to a Ce II transition. We argue that this identification is consistent with the Ce abundance of all the objects discussed in the literature and conclude that in none of the low-mass s-process enriched post-AGB stars there is indication for Li-production. [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 detailTransition probabilities in GdIII
Biémont, Emile ULg; Kohnen, G.; Quinet, Pascal ULg

in Astronomy and Astrophysics (2002), 393(2), 717-720

Theoretical lifetimes, calculated with inclusion of core-polarization effects, have been determined for five 4f(7) 6p levels of doubly ionized gadolinium. They agree quite well with recent experimental ... [more ▼]

Theoretical lifetimes, calculated with inclusion of core-polarization effects, have been determined for five 4f(7) 6p levels of doubly ionized gadolinium. They agree quite well with recent experimental values measured by time-resolved laser-induced fluorescence spectroscopy. From this agreement, the accuracy of a first set of Gd III transition probabilities, calculated for 4f(7) 5d- 4f(7) 6p and 4f(7) 6s- 4f(7) 6p transitions of astrophysical interest, has been assessed. [less ▲]

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See detailLevel lifetimes in 3p and 3d configurations of Fe XII
Biémont, Emile ULg; Palmeri, P.; Quinet, Pascal ULg et al

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2002), 20(1), 37-44

Transitions between the five fine-structure levels in the 3s(2)3p(3) ground configuration of Fe XII (P-like) are of interest in astrophysics and terrestrial plasma diagnostics. The decay rates give rise ... [more ▼]

Transitions between the five fine-structure levels in the 3s(2)3p(3) ground configuration of Fe XII (P-like) are of interest in astrophysics and terrestrial plasma diagnostics. The decay rates give rise to level lifetimes in the millisecond range, which have been measured recently at a heavy-ion storage ring. While most of the 3s(2)3p(2)3d levels are short-lived, two of these levels have no El decay channels and may also have millisecond lifetimes. We present HFR and MCDF calculations of the El, M1, E2 and M2 transition rates between the 3s(2)3p(3), 3s3p(4) and 3s(2)3p(2)3d levels and compare the lifetime results to most recent experimental data as well as to other predictions. [less ▲]

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See detailExperimental and theoretical studies of DyIII: radiative lifetimes and oscillator strengths of astrophysical interest
Zhang, Z. G.; Svanberg, S.; Palmeri, P. et al

in Monthly Notices of the Royal Astronomical Society (2002), 334(1), 1-10

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 ... [more ▼]

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. [less ▲]

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See detailMeasurements of the ground-state ionization energy and wavelengths for the 1snp P-1(1)*-1s(2) S-1(0) (n=4-9) lines of Mg XI and FVIII
Pal'chikov, V. G.; Faenov, A. Y.; Skobelev, I. Y. et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2002), 35(12), 2741-2754

The wavelengths of the 1snp P-1(1)0-1s(2) S-1(0) transitions in the He-like Mg XI (n = 4-9) and F VIII (n = 4-8) have been measured in laser-produced plasmas. The accuracy of the present measurements (0.4 ... [more ▼]

The wavelengths of the 1snp P-1(1)0-1s(2) S-1(0) transitions in the He-like Mg XI (n = 4-9) and F VIII (n = 4-8) have been measured in laser-produced plasmas. The accuracy of the present measurements (0.4-1.6 mAngstrom) is a large improvement over previous results. The Rydberg series is used to determine the ground-state ionization energy of F VIII and Mg XI: E-ion (F VIII) = 953.96 +/- 0.11 eV, E-ion (Mg XI) = 1761.88 +/- 0.15 eV. These experimental results are compared with theoretical data calculated by the 1/Z-expansion method and the HFR and MCDF approaches. Fairly good agreement between theory and experiment is observed with a precision up to 5 x 10(-5). Radiative corrections to the 1s(2) S-1(0) state are analysed and compared with experiments. It is found that QED corrections to the ground-state ionization energy are significant at the present level of experimental accuracy. [less ▲]

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See detailTime-resolved laser-induced fluorescence lifetime measurements and theoretical transition probabilities in Tb III
Biémont, Emile ULg; Garnir, Henri-Pierre ULg; Quinet, Pascal ULg et al

in Physical Review A (2002), 65(5),

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 ... [more ▼]

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. [less ▲]

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See detailLifetime measurements for doubly ionized uranium
Biémont, Emile ULg; Palmeri, P.; Quinet, Pascal ULg et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2002), 35(7), 1701-1705

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 ... [more ▼]

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. [less ▲]

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See detailMeasurement of lifetimes by laser-induced fluorescence and determination of transition probabilities of astrophysical interest in NdIII
Zhang, Z. G.; Svanberg, S.; Palmeri, P. et al

in Astronomy and Astrophysics (2002), 385(2), 724-732

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 ... [more ▼]

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. [less ▲]

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See detailDoubly ionized thorium: Laser lifetime measurements and transition probability determination of interest in cosmochronology
Biémont, Emile ULg; Palmeri, P.; Quinet, Pascal ULg et al

in Astrophysical Journal (2002), 567(2, Part 1), 1276-1283

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 ... [more ▼]

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. [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 detailTime-resolved laser spectroscopy of multiply ionized atoms: Natural radiative lifetimes in CeIV
Zhang, Z. G.; Svanberg, S.; Quinet, Pascal ULg et al

in Physical Review Letters (2001), 87(27),

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 ... [more ▼]

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. [less ▲]

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See detailMeasurement of radiative lifetimes and determination of transition probabilities of astrophysical interest in HoIII
Biémont, Emile ULg; Palmeri, P.; Quinet, Pascal ULg et al

in Monthly Notices of the Royal Astronomical Society (2001), 328(4), 1085-1090

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 ... [more ▼]

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. [less ▲]

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See detailA comparison of the Fe II spectrum of three B[e] stars : HD51585, HD45677 and HD50138
Houziaux, L; Quinet, Pascal ULg

in Eta Carinae and Other Mysterious Stars. The Hidden Opportunities of Emission Spectroscopy (2001)

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