Is Collision-Induced Dissociation of Low-Energy Carbonyl Sulfide Cations Adversely Affected by Asymmetry?

Abstract

We have measured relative abundances of fragment ions resulting from collision-induced dissociation of OCS+ ions in collision with xenon neutrals as a function of ion kinetic energy and scattering angle. The lowest energy dissociation product, S+, dominates at all energies up to 53 eV kinetic energy studied here. Surprisingly, the second most abundant dissociation channel is CS+ and not CO+ even though the thermochemical threshold for CO+ is lower than that for CS+ and CO+ is more abundant than CS+ in the normal mass spectrum of OCS. We do not observe any significant abundance of CO+ in this energy range, suggesting that collision-induced excitation and dissociation of OCS+ is significantly different to that of symmetric triatomic ions. A possible role of asymmetry in the molecular ion's collisional activation via neutral collision is suggested for the different behavior.