Ion-collision spectrometric study of the dissociation dynamics of S₂⁺ and CS⁺ radicals

Abstract

Collision-induced dissociation experiments on ground-state S₂⁺ and CS⁺ have been carried out using a crossed-beam ion translational energy spectrometer with a very high angular resolution (≤10^-4 rad). The distributions of kinetic energies released upon dissociations S₂⁺→S⁺+S, CS⁺→S⁺+C, and CS⁺→C⁺+S in 3-keV collisions with N₂ have been measured; dissociation channels have been identified with the aid of computer simulations of trajectories through the apparatus of ions possessing different center-of-mass kinetic-energy release (K_c.m.) components. In the case of S⁺ formation from S₂⁺, dissociation occurs via excitation to repulsive S₂⁺ electronic states, giving rise to K_c.m. components of 1.5 and 2.0 eV; lower K_c.m. values (0 and 0.3 eV) are obtained upon dissociation of a bound excited state of S₂⁺ by a curve-crossing mechanism. Dissociation of CS⁺ occurs via rotational resonances, giving rise to narrow, symmetrical structure in the S⁺ translational energy spectrum; direct dissociation also occurs which yields relatively high K_c.m. values due to the breaking of the strong C=S triple bond. The CS⁺→C⁺+S channel is considerably weaker.