Is collision-induced dissociation of low-energy carbonyl sulfide cations adversely affected by asymmetry?

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.