Further investigations on doubly excited four-electron ions: beam-foil experiment and MCDF theory

Abstract

In continuation of our previous work on the quintet transitions ls2s2p2 5P-ls2s2p3d 5PO, 5DO, results on other n = 2-n' = 3 quintet transitions for elements N, 0 and F are presented. Assignments have been established by comparison with Multi-Configuration Dirac-Fock ca1culations. High spectral resolution on beam-foil spectroscopy was essential for the identification of most of the lines. For some of the quintet lines decay curves were measured, and the lifetimes extracted were found to be in reasonable agreement with MCDF ca1culations.

First results of experimental and theoretical investigations on sextet states of doubly-excited five-electron ions

“…From our previous studies of doubly-excited three-and four-electron ions [3,4,10] we learned that it is often sufficient to calculate upper and lower states within the manifold of the configurations of their complexes. The comparison of experimental and theoretical transition energies along the isoelectronic sequences even then shows simple trends.…”

“…(1) is a constant. This observation was used, for example, in the investigations on the quintet transitions Is2s2p2 5 P-ls2s2p3d 5 P", 5 DO [3,4]. For almost neutral systems, however, the subsequent hyperbolic terms might become important.…”

“…Most of these observations have been using the beam-foil light source, in which these core-excited states are readily excited. This experimental method was also employed when investigating the quintet states of doublyexcited four-electron ions, the knowledge on which could recently be extended to n = 3 states of several light ions [2][3][4].…”

“…At present our calculation includes only the configurations of the complexes of the levels involved. This is a shortcoming, but our previous investigations [3,4] have shown that already this approximation can provide meaningful data for a comparison of theoretical and experimental transition energies along the isoelectronic sequence; such an analysis is a most useful tool which aids the identification of transitions. During the course of our investigation theoretical results obtained by Brage and Miecznik [9] when using…”

The Allure of High Total Angular Momentum Levels in Multiply-Excited Ions

“…Nicolaides (for example, Reference [47]), by N. Vaeck and her colleagues, and by J.H. Blanke (on three-to five-electron ions) [48][49][50][51] for computations and further literature references on core-excited levels. These theoretical studies apply a wide variety of computational approaches to atomic structure, from nonrelativistic to fully relativistic, from configuration interaction to many-body perturbation theory, R-matrix, saddle-point, and complex rotation.…”