On the origin of the CO+ ion in resonant multiphoton ionization of CO2

Multiphoton ionization of CO2 via three-photon resonances with the (2Пg,Ω)nf Rydberg states results in production of CO+2, CO+, and O+ ions. This study explores the branching into CO+2 and CO+ ion channels and its laser power dependence for the levels nf = 5–7. The results indicate that either a significant fraction of the CO+2 ions produced in the initial ionization step do not participate in a dissociative two-photon transition or that dissociation of low vibrational levels of the parent ion occurs by a transition to a state with a lifetime on the order of 600 ps. A method of measuring predissociation lifetimes by determining the fraction of population which survives a saturated transition to a dissociative state is suggested.