Electron impact dissociative ionisation of hydrogen, water and hydrogen sulphide

The dissociative ionisation of H 2 , H 2 O and H 2 S by electron impact was investigated between electron impact energies of 20 and 45 eV. Protons were the detected fragments, and a time-of-flight method was used to measure the proton kinetic energies. By measuring thresholds for the production of discrete energy groups of protons, it was possible to determine the dissociation limits and kinetic energy distributions for individual electronic states. It was found that autoionising states that lead to dissociation were the major contributors of proton fragments for all of the molecules investigated.