Reference-free measurements of the 1s 2s 2p 2PO1=2;3=2 ! 1s2 2s 2S1=2 and 1s 2s 2p 4P5=2 ! 1s2 2s 2S1=2 transition energies and widths in lithiumlike sulfur and argon ions

We have measured the widths and energies of the 1s2s2p 2 P 1/2,3/2 → 1s 2 2s 2 S 1/2 transitions in lithiumlike sulfur and argon, as well as the energies of the forbidden 1s2s2p 4 P 5/2 → 1s 2 2s 2 S 1/2 M2 transition in both elements. All measurements were performed with a double-flat crystal spectrometer without the use of any reference line. The transition energy measurements have accuracies ranging from 2.3 ppm to 6.4 ppm depending on the element and line intensity. The widths and the intensity ratios of the 1s2s2p 2 P 1/2,3/2 → 1s 2 2s 2 S 1/2 lines have also been measured. These are the first reference-free measurements of transitions in core-excited lithiumlike ions, and have an accuracy comparable to the best relative measurements. We have also performed multi-configuration Dirac-Fock calculations of the widths, energies and intensity ratios. Extensive comparison between existing experimental results and theory is performed, and Bayesian techniques employed to extract the energy of the 1s 2p 2 4 P 1/2 → 1s 2 2p 2 P 1/2 transition in sulfur and identify contaminant transitions

Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence

Energies of 5l_j (l= s, p, d, f, g) and 4f_j states in neutral Ag and Ag-like ions with nuclear charges Z = 48 - 100 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are calculated for the 17 possible 5l_j-5l'_{j'} and 4f_j-5l_{j'} electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with Z60. Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory.Comment: 8 page

Relativistic K shell decay rates and fluorescence yields for Zn, Cd and Hg

In this work we use the multiconfiguration Dirac-Fock method to calculate the transition probabilities for all possible decay channels, radiative and radiationless, of a K shell vacancy in Zn, Cd and Hg atoms. The obtained transition probabilities are then used to calculate the corresponding fluorescence yields which are compared to existing theoretical, semi-empirical and experimental results

Relativistic transition wavelenghts and probabilities for spectral lines of Ne II

Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4 3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics (QED) corrections. The results are compared with all existing experimental and theoretical data

RELATIVISTIC EFFECTS IN THE CALCULATION OF OSCILLATOR STRENGTHS : "AB INITIO" METHODS

On décrit brièvement les méthodes utilisées pour inclure l'influence des effets relativistes dans les calculs des forces d'oscillateurs. Les principales modifications introduites par la prise en compte de ces effets sont étudiées à l'aide de quelques exemples empruntés aux calculs les plus récents.The methods used to introduce relativistic effects in the calculation of oscillator strengths are briefly reviewed. The main modifications induced by these effects are analyzed by considering some typical examples taken from recent calculations

Dirac-Fock one-centre expansion calculations on the molecular model systems ThH4 and UH6

On présente certains résultats de calculs relativistes Dirac-Fock à un centre pour les systèmes modèles ThH4 et UH6. Les hybridations, les distributions radiales et l'influence des 5f sur la distance de liaison sont discutées. Une valeur de 30 pm est prédite pour la contraction actinidique.Relativistic Dirac-Fock one-centre expansion calculations are presented for the molecular model systems ThH4 and UH6. The hybridizations, the radial distributions and the effect of the 5f : s on the bond length are discussed. A value of 30 pm is predicted for the actinoid contraction

MCDF CALCULATIONS OF TRANSITION ENERGIES IN URANIUM HELIUMLIKE IONS

Les résultats de calculs ab initio pour les énergies de transition dans l'ion héliumoïde de l'uranium sont donnés. La méthode MCDF a été utilisée pour traiter efficacement des effets relativistes et des corrélations. L'importance des corrections radiatives pour ce système fortement relativiste est discutée. Des effets de retard intenses sont prédits par les calculs sur certains niveaux.Ab initio calculation results are reported for transition energies in uranium heliumlike ions. The MCDF method is used to treat relativistic effects and correlations efficiently. Radiative corrections for this highly relativistic system are discussed. Important retarded interaction effects are also encountered for some levels