Direct observation of orbit rotation predissociation in the O2 Schumann–Runge system

Laser induced predissociation fluorescence spectroscopy was performed with a tunable Argon fluoride laser in the Schumann–Runge band of O2 in an open atmospheric flame. Simple rotationally resolved spectra of the 10←2 and 11←2 bands were obtained when the fluorescence was dispersed through a monochromator. Line widths of these transitions, which predominantly reflect state specific predissociation, were measured. It was found that the orbit rotation interaction between the B 3Σ−u state and the 3Πu continuum must be included in addition to the spin–orbit interaction between B 3Σ−u and 5Πu, 1Πu, 3Σ+u, and 3Πu in order to fit the data. The general coupling formulas for orbit–rotation interaction for the case of intermediate coupling between Hund’s case a and b were derived and orbit–rotation interaction constants for v=10 and 11 were estimated. This is the first experimental evidence of the orbit rotation interaction in the O2 Schumann–Runge system.