Ion Impact Spectroscopy: Inelastic Scattering of 150–500-eV H+ and H2+ from N2, CO, C2H2, and C2H4

Abstract

A high‐resolution ion impact spectrometer has been constructed to measure the energy lost by ions which have been inelastically scattered from molecular targets. Inelastic collisions between 150–500‐eV H⁺ and H₂⁺ and N₂, CO, C₂H₂, and C₂H₄ were observed in which the energy lost corresponded to electronic transitions in the target molecules. Most of the observed energy losses were assigned to known transitions in the targets. The cross sections for the observed electronic excitations are large. Ion impact excitation in the cases studied appears to be a very specific process because only certain types of transitions are excited in molecules which have a large number of available electronic states. Proton impact was found to excite only singlet–singlet transitions while H₂⁺ impact preferentially excited certain types of singlet–triplet transitions. The implications of the specific nature of the observed excitation as well as the general spectroscopic utility of the method are discussed.