Excitation-autoionization cross sections and rate coefficients for Ga-like ions

Abstract

Results of cross-section and rate coefficient calculations for electron impact direct and indirect ionization of ions belonging to the GeI isoelectronic sequence (ground 3d104s24p2) are presented. The cross-sections are given at near threshold energies for the five ions Kr4+, Mo10+, Xe22+, Pr27+ and Dy34+. The rate coefficients are computed for all the ions from Kr4+ to U60+ in the GeI sequence at seven electron temperatures (kTe = 0.1EI, 0.3EI, 0.5EI, 0.7EI, EI, 2EI and 10EI, where EI is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated with the Lotz formula approximation and the contributions of excitation-autoionization (EA) calculated in the framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is shown as a function of Z along the GeI isoelectronic sequence.