Transitions between quintet states of doubly excited four-electron ions: experiment and MCDF theory along the isoelectronic sequence

Abstract

Following an earlier observation in F VI we identified the line pair Is2s2p2 5p-Is2s2p3d 5p o , 5D o for the elements N, 0, Mg, and tentatively for Al and Si in beam-foil spectra. Assignment was established by comparison with Multi-Configuration Dirac-Fock calculations along the isoelectronic sequence. Using this method we also identified some quartet lines of lithiumlike ions with Z > 10.

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

“…O [14] we studied the transition Is2s2p2 5P-ls2s2p3s 5P": As diseussed in the theoretieal part, we do not expeet any near perturbers to have a notable influenee on the states Is2s2p3s 5P" and Is2s2p3d 5P"; 5D O (Fig. 1).…”

“…In addition, the transitions Be I 1s2s2p3p 5P: IS2p2 3p 5So and Is2s2p4p 5P-l s2p24p 5So ha ve been observed [12,13]. In an earlier paper [14] we reported the identification of the Is2s2p2 5P-Is2s2p3d 5P"; 5DO transitions, for elements N, 0, Fand Mg, which have been identified by comparing experimental transition energies with theoretical ones obtained with the M ulti-Configuration Dirac-Fock program of Desclaux [15,16].…”

“…However, according to the calculations by Chen [19], autoionization and intercombination decay to singly excited states can be neglected for the elements considered here. fulfilled for the transitions Is2s2p2 5P-Is2s2p3d 5P", 5Do by the transition Is 22p 2po-ls 23d 2D [14,28]. Thus the window parameters ean be kept fixed in the appropriate fitting proeedure.…”

“…This mixing will destroy the linearity of the correlational part of the transition energies along an isoeleetronic sequence. This eoncept was previously used für the identification of many quartet lines [14,17], the quintet transitions ls2s2p2 5p-ls2s2p3d 5p o, 5Do [14] and for the line ls2s2p2 5P-ls2s2p3s 5P" as diseussed in Seetion 4. The concept of our approach is to calculate the correlation energies of the upper states explicitly.…”

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.…”