Simultaneous and Induced Electronic Transitions in Oxygen. II

Abstract

A general theory of the oscillator strengths of the three bimolecular transitions, 1 Σ g + 3 Σ g − ← 3 Σ g − 3 Σ g − , 1 Σ g + 1 Δ g ← 3 Σ g − 3 Σ g − , and 1 Σ g + 1 Σ g + ← 3 Σ g − 3 Σ g − , in oxygen is given. The intensity of these three transitions is assumed to be derived from the allowed transitions due to mixing of the electronic terms through the intermolecular interaction. The theoretical techniques developed in Paper I of this series are used. No particular geometry for the O2···O2 pair is assumed. All electrons are included in the theory and all the interactions, allowed in the absence of intermolecular overlap, are considered. Two experimentally significant points emerge from this work. (1) Each of these three transitions should be considerably weaker than either of the two transitions 1 Δ g 3 Σ g ← 3 Σ g − 3 Σ g − and 1 Δ g 1 Δ g ← 3 Σ g − 3 Σ g − discussed in Paper I. This is because while the latter transitions can borrow from several allowed transitions, including the strongly‐allowed π–π transitions, the former can borrow only from transitions involving π–σ excitation which are expected to be at higher energy and to have relatively small oscillator strengths. (2) The relative oscillator strengths of these three transitions considered here agree fairly well with experiments.