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 ³Π_u continuum must be included in addition to the spin-orbit interaction between B ³Σ^-_u and ⁵Π_u, ¹Π_u, ³Σ⁺_u, and ³Π_u 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.