Laser-induced fluorescence of the B 2Σ+– X 2Π i system of OH: Detection of v ′′=8 and 9

The previously unobserved B 2Σ+–X 2Πi electronic system of OH is detected by laser-induced fluorescence in a low-pressure flow system. OH is produced in high vibrational levels of the ground electronic state by the H+O3 reaction. Light from a frequency-doubled tunable dye laser excites the radical via the (0,8), (0,9), and (1,8) bands of the B 2Σ+–X 2Πi transistion at 225, 236, and 221 nm, respectively. The fluorescence is detected in the B 2Σ+–A 2Σ+ system in the visible and near ultraviolet. Measured emission intensities in the (0,3) to (0,9) and the (1,3) to (1,9) bands of B–A are in good agreement with previous theoretical calculations. The experimental branching ratio for emission between the B–A (0,3) and B–X (0,10) bands is about three times larger than theoretically predicted. Detection of high-lying vibrational levels in the electronic ground state, v′′=6 through 15, for experiments in collision dynamics and reaction kinetics, is feasible using the B–X system.