Direct Dissociative Excitation of Heteronuclear and Homonuclear Ions of Inert Gases by Electron Impact

摘要

A theoretical description of the process of dissociative excitation of a molecular ion by an electron impact under the condition of effective population of a large number of its vibrational-rotational levels has been given. The approach is based on the quantum version of the theory of non-adiabatic transitions between electronic terms of a molecular ion and on the replacement of the summation with respect to vJ-levels with the integration with respect to v and J. Semi-analytical formulas for the integral contribution of the entire vibrational-rotational quasicontinuum to the cross sections sigma(de)(T) (epsilon) and rate constants alpha(de) (T,T-e) of the process under study in a plasma with the and temperatures of its electronic and ionic components have been obtained. The developed theory has been used to study the processes of dissociative excitation of heteronuclear (HeXe+ and ArXe+) and homonuclear (Ar-2(+) and Xe-2(+)) ions of inert gases. A strong dependence of the results on the ion dissociation energy and large differences in the behavior and characteristic values of sigma(de)(T) (epsilon) and alpha(de) (T, T-e) for these systems in different energy, epsilon, and temperatures, T-e and T, has been established. The regions of dominance of the contributions of two competing channels: direct dissociative excitation and dissociative recombination to the total cross sections and the rate of destruction of molecular ions of inert gases by electron impact have been determined. The analysis of the behavior of the differential rate constants of dissociative excitation in a unit electron energy interval in the final reaction channel has demonstrated qualitative differences in the dynamics of this process in the cases of weakly and moderately bound molecular ions.