Electron ionization of CO 2

Abstract

Relative partial ionization cross-sections (PICS) and precursor-specific relative partial ionization cross-sections for fragment ions formed by electron ionization of CO 2 have been measured using time-of-flight mass spectrometry (TOFMS) coupled with a 2-D ion-coincidence technique. We report data for the formation of C +, O +, CO +, C 2+, O 2+ and CO 2 2+ relative to the formation of CO 2 +, as a function of ionizing electron energy from 30 to 200 eV. This data includes, for the first time, measurements on the formation of ion triples by dissociative multiple ionization of CO 2 by electrons. Our analysis of the 2-D coincidence spectra provides new information on the dynamics and energetic of charge separating dissociation of the CO 2 dication and trication. Through determinations of the kinetic energy release (KER) involved in ion pair formation, we also conclude that indirect double ionization processes contribute significantly to the yield of CO + + O + ion pairs at ionizing electron energies below 55 eV.