On the mechanism of dissociative and double photoionization in CO

Abstract

Observed branching ratios for dissociative ionization (C+ and O+) and double ionization (CO2+ and C2+) have been differentiated with respect to the incident photon energy in the region between their thresholds and 130 eV. The method provides a new photoion spectroscopy of which results indicate the dissociative ionization and the double ionization channels for the respective ions. The mechanism producing these ions is discussed in the light of the reported energy states of CO+ and CO2+ such as the multielectron bands [C 2Σ+, D 2Π, F, G 2Σ+, and 2Σ+(3σ)−1] and the double ionization states [(5σ−1, 1π−1), (4σ−1, 5σ−1), (5σ−2), (1π−2), (4σ−1, 1π−1), (4σ−2), (3σ−1, 5σ−1), (3σ−1, 1π−1), (3σ−1, 4σ−1), and (3σ−2)] observed in the Auger spectra. It becomes evident that these states play a significant role in producing the fragmented ions. The thermochemical thresholds for various dissociation channels are listed from the known energy levels of the separated atoms and ions in order to deduce the possible energy states of the dissociated fragments.