Molecular dissociation by electron impact: High Rydberg fragments from methane, ethylene, and ethane

Abstract

Electron impact dissociation of CH4, C2H4, and C2H6 produces high Rydberg H and C fragments. Time-of-flight measurements and excitation functions help to characterize the molecular processes involved. Although details differ, the three molecules display similar dissociation behavior; relatively low kinetic energy fragments (≲8 eV) arise from states between 19 and 30 eV, higher kinetic energy fragments from states between 30 and 40 eV (states most likely with doubly ionized cores), and even higher kinetic energy fragments (up to 18 eV) from states above 40 eV. Comparisons of high Rydberg kinetic energy spectra with available ion kinetic energy spectra show general agreement confirming the utility of the core ion model for polyatomic molecules.