Collision-induced fragmentation of triatomic ions

Abstract

A method for identifying energy states of the products of ion dissociations using ion kinetic energy spectrometry is described. The reactant triatomic ions at relative translational energies of 8 keV are allowed to undergo collision-induced dissociation and the positions of the peak maxima of the kinetic energy spectra are used to measure the excitation energy acquired by the ion during the vertical transition from the ground ionic state to the reactive surface. The kinetic energy released on fragmentation is determined from the peak shape and subtracted from the energy of the energized ion to fix the energy of the products. The large range of energies usually released suggests that reaction generally occurs on a repulsive surface. The following product states are deduced for the reactions listed: ▪ Except for the HCN + reaction, the reacting states correlate with ground state diatomic ions and ground state diatomic molecules, although the neutral atoms and atomic ions are not necessarily formed in the ground electronic states. The assigned product states formed by collisional excitation correlate with reacting states which are spin allowed. Without exception, larger kinetic energy releases are associated with the process for which the positive charge resides with the diatomic fragments. The COS + ion reacts via three pathways to give CS + , S + and CO + as the charged fragments. The first two reactions are unexceptional. The last reaction is apparently due to COS + in an electronically excited state reached prior to collision since the measured kinetic energy loss corresponds to an excitation energy which is 3.8 eV less than that required to reach the dissociation limit leading to CO + + S in their ground electronic states.