Coupled diabatic configuration interaction treatment of the O2 B′–X transition including computation of predissociation linewidths, optical f values, and generalized oscillator strengths

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Abstract
A b initio CI (configuration interaction) calculations are carried out for O2 in various 3Σ−u excited states in order to study the avoided crossing that is responsible for the discrete B′–X bands found in the high-energy region of the Schumann–Runge continuum. A diabatic transformation is carried out which allows for the description of nonadiabatic effects in this spectral range. A coupled vibrational treatment is employed in conjunction with the complex scaling technique in order to compute the predissociation linewidths of the B′ levels, and these results are found to be in good agreement with experiment, particularly for trends observed between different isotopomers of this system. Optical f values and generalized oscillator strengths (GOS) are calculated for a series of vibrational transitions and are also found to compare well with measured data. The observed finding that the GOS varies quite slowly with K2 for the 0–0 transition, but decreases rather sharply for the 1–0 species is reproduced in the calculations and the behavior of this property for other transitions is predicted.