Ion kinetic energy spectroscopy of the doubly charged ion of carbon monoxide

Abstract

Spontaneous and collision-induced dissociation processes of CO2+ ions, formed by electron impact, have been studied in a double-focusing mass spectrometer using techniques of ion kinetic energy spectroscopy. The predissociation process, responsible for unimolecular dissociation of CO2+ on the microsecond time scale, is almost certainly electronically adiabatic tunneling through a potential barrier, though predissociation via electronic curve crossing cannot be entirely ruled out. Semiempirical potential curves for states of CO2+ were revised in order to better accommodate all of the available data, including Auger spectra, appearance energies, and kinetic energy release. Collision induced dissociation processes with Ar, N2, and H2 proceed via charge exchange, and involve predissociation of the D 2Π state by the C 2Δ state of CO+. When He is used as collision gas, the dissociation processes involving charge exchange are different, and require an energetic contribution from the relative kinetic energy (kinetic energy loss). In addition, He is quite different in inducing dissociation of CO2+ without prior charge exchange, from states of CO2+ up to 13 eV above the dissociation limit.