Overview of the inner-subshell excitations n0l0nl included in the present calculations

Table 2. Overview of the inner-subshell excitations n0l0nl included in the present calculations. All subshells with quantum numbers nl, where nnmax and llmax, providing at least one vacancy to which the n0l0 electron can be excited were considered. The orbital quantum numbers l0, lmax = 0, 1, 2, ... are expressed by their spectroscopic symbols s, p, d,..., respectively. For ions in the ground-state configuration, m is the number of electrons in the 4d subshell. It is equal to 10 for Sn4 + and 1 for Sn13 +. As far as long-lived excited ions are concerned, we only had to consider 4d-subshell-excited configurations for the charge states up to q = 12. In the configurations of interest, the 4d subshell is initially populated with m − 1 electrons and the excited electron is initially in subshell n1l1. The subshells n1l1 taken into account in the present analysis are listed in table 1. For the case of Sn13 +, the only excited configuration of relevance to the present measurements is the 4p54d2 configuration.

Abstract

Electron-impact single-ionization cross sections of Snq + ions in charge states q = 4–13 with 4d[10 − (q − 4)] outer-shell configurations have been studied in the energy range from the corresponding thresholds up to 1000 eV. Absolute cross sections and fine-step energy-scan data have been measured employing the crossed-beams technique. Contributions of different ionization mechanisms have been analysed by comparing the experimental data with calculations employing the configuration-averaged distorted wave approximation. Ionization plasma rate coefficients inferred from the experimental data are also presented.