Effect of third- and fourth-order moments on the modeling of Unresolved Transition Arrays

The impact of the third (skewness) and fourth (kurtosis) reduced centered moments on the statistical modeling of E1 lines in complex atomic spectra is investigated through the use of Gram-Charlier, Normal Inverse Gaussian and Generalized Gaussian distributions. It is shown that the modeling of unresolved transition arrays with non-Gaussian distributions may reveal more detailed structures, due essentially to the large value of the kurtosis. In the present work, focus is put essentially on the Generalized Gaussian, the power of the argument in the exponential being constrained by the kurtosis value. The relevance of the new statistical line distribution is checked by comparisons with smoothed detailed line-by-line calculations and through the analysis of 2p-3d transitions of recent laser or Z-pinch absorption measurements. The issue of calculating high-order moments is also discussed (Racah algebra, Jucys graphical method, semi-empirical approach ...).Comment: submitted to High Energy Density Physic

UTA versus line emission for EUVL: Studies on xenon emission at the NIST EBIT

Spectra from xenon ions have been recorded at the NIST EBIT and the emission into a 2% bandwidth at 13.5 nm arising from 4d-5p transitions compared with that from 4d-4f and 4p-4d transitions in Xe XI and also with that obtained from the unresolved transition array (UTA) observed to peak just below 11 nm. It was found that an improvement of a factor of five could be gained in photon yield using the UTA rather than the 4d-5p emission. The results are compared with atomic structure calculations and imply that a significant gain in efficiency should be obtained using tin, in which the emission at 13.5 nm comes from a similar UTA, rather than xenon as an EUVL source material

Effects of configuration interaction on atomic hyperfine structure in lN l' configurations

The effects of configuration interaction on hyperfine structure (hfs) are considered using second-order perturbation theory. Following a first paper which deals with lN configurations, this paper concerns the case of lN l' configurations. Effective operators, which describe the crossed second-order effects of electrostatic and hyperfine interactions, are given for all types of excitations. If N ≥ 2 and |l-l'| = 0 or 2, three-electron effective operators occur for excitations of the type l ←→ l'. The formalism is applied to the case of 3 dN 4 s configurations, for which tables of the Δl, ΔsC and Δ q factors are given. Comparisons with experimental results are given for the first series of transition metals ; elsewhere such comparisons are limited by the scarceness of experimental data available. An appendix indicates a few corrections to the first paper.Les effets de l'interaction de configuration sur la structure hyperfine sont traités en utilisant le second ordre de la théorie des perturbations. Dans un premier article, le cas des configurations lN avait été envisagé. Nous traitons maintenant le cas général des configurations de type lN l' . Les expressions des opérateurs effectifs qui représentent les termes de second ordre croisé de l'énergie coulombienne et des effets hyperfins ont été obtenues pour les différents types d'excitations qui peuvent intervenir. Dans le cas N ≥ 2 et |l- l'| = 0 ou 2, des opérateurs à trois particules apparaissent, lorsqu'on considère les excitations l ←→ l'. Ce formalisme est appliqué au cas des configurations 3 dN 4 s, pour lesquelles on donne les tables des facteurs Δl, ΔgC et Δq. Des comparaisons expérimentales sont présentées pour la première série des métaux de transition. Pour l'instant de telles comparaisons sont limitées par le manque de résultats expérimentaux connus. Dans un appendice, on indique quelques corrections à l'article traitant le cas des configurations l N

THEORETICAL INVESTIGATIONS ON RESONANCE TRANSITIONS IN THE NEON- AND NICKEL-LIKE IONS AND THEIR SATELLITES

La méthode du potentiel paramétrique relativiste a été utilisée pour interpréter les raies de résonance des ions isoélectroniques du néon et leurs satellites émis par des ions de moindre charge. Les faisceaux de transitions entre sous-configurations construites sur le même niveau du coeur 2p5 avec deux ou trois électrons spectateurs n=3 sont prévus a priori, dans le formalisme des faisceaux de transitions non résolus (UTA). L'accord est satisfaisant avec les données expérimentales relatives aux éléments entre le baryum et le praséodyme. Un spectre de l'argent produit par irradiation laser au GRECO-ILM (Gauthier, Geindre et Monier, 1985) est analysé et les transitions de Ag XXXVIII et Ag XXXVII sont identifiées . Les transitions quadrupolaires électriques 2s-3d dans la séquence isoélectronique du néon et 3p-4f dans la séquence isoélectronique du nickel sont identifiées expérimentalement dans les spectres de plasmas laser, offrant de nouvelles perspectives de diagnostics.The resonance lines of neon-like ions and their long-wavelength satellites emitted by ions of lower charge are interpreted by means of the relativistic parametric potential method. The transition arrays between sub-configurations with the same angular momentum of the 2p5 core and two or three n=3 electrons added are predicted ab initio in the UTA formalism and fit the experimental data from barium to praseodymium. A spectrum of laser-irradiated silver recorded by Gauthier, Geindre and Monier at GRECO-ILM facilities is shown with detailed identification of Ag X X X V I I I and Ag XXXVII transitions from 3.2 to 4.2 Å. The electric-quadrupole transitions 2s-3d in the neon sequence and 3p-4f in the nickel sequence have been observed in laser-produced plasmas and open the way to new diagnostics

Comparison between magnetic-hyperfine-structure parameters in Sci and TII

Ab initio calculations of the second-order effects of the configuration interaction on the orbit-dependent magnetic-hyperfine-structure parameters in the 3dN 4s2 configuration have been performed. The importance of the contributions of the different excitations is discussed and a comparison is made between Sc and Ti. The ratio α = a1/a sC is found to be 1.07 and 1.05 in Sc and Ti respectively.Les effets de second ordre dus à l'interaction de configuration sur les paramètres concernant les parties de structure hyperfine magnétique dépendant de l'orbite ont été évalués a priori dans les termes fondamentaux du Scandium et du Titane. Les importances relatives des différentes excitations sont discutées. Les valeurs du rapport α = a1/asC obtenues dans Sc et Ti sont respectivement 1,07 et 1,05