Calculations for 1s²3l3l' states in C²⁺, N³⁺, O⁴⁺, Ne⁶⁺and Xe⁵⁰⁺

Abstract

Calculations are presented of energy level values, radiative transition probabilities and autoionisation rates for terms belonging to the ls23/31' configurations for several ions in the Be I isoelectronic sequence (C2+, N3+, 04+, Ne6+ and Xe5"+). The results of a C I calculation including the configurations of the complex (and the 3d4f configuration) are compared with experimental results obtained in collisions of highly stripped ions with He, H 2 and Ar and with the results of theoretical calculations.

Calculations for doubly-excited states populated in two-electron processes

“…In a hydrogenic approximation the autoionization rate is independent of Z [16] and in reality, the autoionization rates for the Be isoelectronie sequence have been found to be fairly independent of Z over the range C 2÷ to Xe 5°÷ [14]. Thus we expect the end result to be a degree of radiative stabilization with increasing Z.…”

Calculations of decay rates for triply-excited states in N2+

“…We have used the arithmetic average energy for the odd and even configurations to determine the free electron energy since the large mixing makes it difficult to identify particular terms with particular configurations. We assume that the variation in rates with energy is small for the rather high free-electron energies involved, as already found for the ls23e3t ' terms [7]. In order to check the validity of the average approach [3,4] for this type of configuration, we have also calculated the average autoionization rates for the ls23e3e'3e '' configurations individually and evaluated the radiative decay rates (A') to all the Is23e3e'2e ' ' terms.…”

“…As for the previous calculations on the ls23f3£ ' terms in ha+ [7], the basis set includes all the configurations belonging to the Layzer complex 3e3e'3e" [8] but in addition all the configurations of the type 3e3e'4e". The lowest of these lie in the same range of energy as the highest 3e3e'3e" states.…”

“…In view of this result, we have checked whether single configuration calculations of average values give a correct picture of the behaviour of the autoionization decay rates of the 3 e 3 e ' 3 r ' triply-excited configurations. At the same time we have calculated the average radiative decays to the l s 2 3 t 3 t ' 2 t '' states which are known to be weakly dependent on the particular term for the doubly-excited states [7].…”

From atoms to biomolecules: a fruitful perspective

“…Double capture is by far the most studied experimentally and theoretically [161] mainly because of the possibility to also reach those doubly-excited states radiatively from the ground state [16,62]. Note that this research area is still very active, as illustrated by the recent reinvestigation of our pioneer work [161] on radiative transition probabilities and Auger rates of the 1s 2 3'3' 0 states in Be-like ions [147]. The capture of three electrons from the neutral target into triply excited states is also possible but the analysis of the resulting electron spectra is much more complicated due to the complexity of the Auger decay cascade of the triply excited states.…”