Single to quadruple ionization ofCO2due to electron impact

Abstract

The electron-impact multiple ionization and the subsequent dissociation of ${\mathrm{CO}}_{2}$ have been studied for electron energies from the threshold to 600 eV. The dissociation channels of up to quadruply ionized carbon dioxide molecules have been identified. The absolute cross sections for the ion-pair dissociation channels in double, triple, and quadruple ionization of ${\mathrm{CO}}_{2}$ have been obtained. The absolute cross sections of the other channels involving neutral fragments are also derived. The experiment shows that the total cross section of single, double, and triple ionization decreases by at least an order of magnitude as the ionization stage increases by 1. By studying the structure of the islands in the covariance maps, we have concluded that one of the ${\mathrm{CO}}_{2}^{2+}$ dissociation channels ${\mathrm{CO}}_{2}^{2+}\ensuremath{\rightarrow}{\mathrm{C}}^{+}{\mathrm{}+\mathrm{O}}^{+}\mathrm{}+\mathrm{O}$ is dominated by the process of secondary decay. The dissociation channel ${\mathrm{CO}}_{2}^{2+}\ensuremath{\rightarrow}2{\mathrm{O}}^{+}\mathrm{}+\mathrm{C}$ is a concerted process. The three-body dissociation channels of triply ionized carbon dioxide are found to be dominated by concerted processes no matter how the charges are distributed on the fragments. The momentum distribution on the fragments can only be explained by the charge mobility during the dissociation process of the triply ionized molecules. The metastable decay of ${\mathrm{CO}}_{2}^{2+}$ is also observed directly.