Dissociative-ionization cross sections for 12-keV-electron impact on CO2

Abstract

The dissociative ionization of a CO2 molecule is studied at an electron energy of 12 keV using the multiple ion coincidence imaging technique. The absolute partial ionization cross sections and the precursor-specific absolute partial ionization cross sections of resulting fragment ions are obtained and reported. It is found that ∼75% of single ionization, 22% of double ionization, and ∼2% of triple ionization of the parent molecule contribute to the total fragment ion yield; quadruple ionization of CO 2 is found to make a negligibly small contribution. Furthermore, the absolute partial ionization cross sections for ion-pair and ion-triple formation are measured for nine dissociative ionization channels of up to a quadruply ionized CO2 molecule. In addition, the branching ratios for single-ion, ion-pair, and ion-triple formation are also determined. © 2011 American Physical Society.