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.