The transition probability of electron loss from anions in the gas phase: The lifetime of O2 ⋅−

Abstract

The unimolecular primary chemical process, A−→A+e−, is investigated from a theoretical and computational point of view. A ‘‘standard’’ procedure for calculating the lifetime of A− directly is proposed based on the quantum mechanical transition probability. Specific application of the standard procedure is made to electron loss from O ⋅−2. The lifetime of O ⋅−2(ν′=4) calculated with the proposed method is 36×10−12 s, in good agreement with experimental data. An improvement to the standard procedure yields the best theoretical estimate for the lifetime, 125×10−12 s. The lifetimes of O ⋅−2 at higher vibrationally excited states are also calculated and agree well with those of previous calculations. The dependence of the calculated lifetime on the geometric and vibrational parameters of O2 and O ⋅−2 is discussed.