Electron ionization of hydrogen sulfide

Abstract

Precursor-specific relative partial ionization cross sections, for all the different fragment ions formed by electron ionization of hydrogen sulfide, have been measured using time-of-flight mass spectrometry coupled with a two-dimensional ion coincidence technique. Relative cross sections are reported for ionizing energies from 30 to 200 eV. These cross sections allow the contribution from single, double and triple ionization to the individual fragment ion yields, following ionization of hydrogen sulfide, to be quantified. To compare our data with the literature we reduce our precursor-specific cross sections, by summing them for each fragment ion, to generate relative partial ionization cross sections. Following this data reduction, good agreement is found between our data and one set of recently published absolute partial ionization cross sections, but discrepancies are observed with another set of recently published data. Our analysis shows that the contribution of double ionization to the total ion yield reaches a maximum of 20% at 100 eV. Given the lack of available information on the fate of the excited electronic states of H 2S 2+, we have extracted kinetic energy releases for the various dicationic fragmentation channels from our coincidence data. From these kinetic energy releases, estimates of the energies of the electronic states of H 2S 2+ which are responsible for the different fragmentation channels can be made. These estimates, in comparison with other data on the electronic states of H 2S 2+, reveal the population of excited states of H 2S 2+ at electron energies above 50 eV. At ionizing electron energies above 50 eV, a significant proportion of the major dissociation channels of H 2S 2+ appear to involve the population of excited electronic states.