Radiative 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

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 ▲]

Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar+

in Physical Review Letters (2007), 99

A laser probing investigation has yielded the lifetimes of the 3s23p41D3d 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 ... [more ▼]

A laser probing investigation has yielded the lifetimes of the 3s23p41D3d 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 independenttheoretical 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. [less ▲]

Radiative lifetime and oscillator strength determinations in potassium ions (K V, K VI and K VII)

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 ▲]

Radiative lifetimes, branching fractions and oscillator strengths in PdI and the solar palladium abundance

in Astronomy and Astrophysics (2006), 452(1), 357-362

Transition probabilities have been derived for 20 5s-5p transitions of Pd I from a combination of radiative lifetime measurements for 6 odd-parity levels with time-resolved laser-induced fluorescence ... [more ▼]

Transition probabilities have been derived for 20 5s-5p transitions of Pd I from a combination of radiative lifetime measurements for 6 odd-parity levels with time-resolved laser-induced fluorescence spectroscopy and of branching fraction determination using a hollow cathode discharge lamp. Additional oscillator strengths for 18 transitions have been determined from measured lifetimes and theoretical branching fractions obtained from configuration interaction calculations with core-polarization effects included. These new results have allowed us to refine the palladium abundance in the solar photosphere: A(Pd) = 1.66 +/- 0.04, in the usual logarithmic scale, a result in close agreement with the meteoritic value. [less ▲]

Radiative lifetimes and transition probabilities in TaI

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2006), 37(1), 29-35

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 ... [more ▼]

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. [less ▲]

Transition probabilities and lifetimes in singly ionized rhenium

in Monthly Notices of the Royal Astronomical Society (2005), 362(4), 1348-1352

Transition probabilities and radiative lifetimes have been obtained for 45 transitions of Re II using a combination of radiative lifetime values obtained with the laser-induced fluorescence technique ... [more ▼]

Transition probabilities and radiative lifetimes have been obtained for 45 transitions of Re II using a combination of radiative lifetime values obtained with the laser-induced fluorescence technique ( seven levels) and theoretical branching fractions. This new set of results, concerning ultraviolet and visible lines, will be useful in the future for investigating the composition of chemically peculiar stars. [less ▲]

On the importance of an M2 depopulating channel for a KrII metastable state

in Physical Review Letters (2004), 93(6),

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 ... [more ▼]

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. [less ▲]

Level lifetimes in 3p and 3d configurations of Fe XII

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 ▲]

Measurements 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

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 ▲]

Measurement of lifetimes by laser-induced fluorescence and determination of transition probabilities of astrophysical interest in NdIII

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 ▲]