Photolysis of HOCl at 248 nm in a supersonic molecular beam: laser-induced fluorescence spectra of OH

Abstract

The nascent OH rotational distribution has been observed following the 248 nm photolysis of HOCl in a supersonic molecular beam. A strong preference for the population of the OH 2Π3/2 spin state is found and a significant deviation from the statistical population of the OH lambda-doublet states is observed. The OH rotational distribution can be characterised by a temperature which is slightly different for the two spin–orbit states. These rotational temperatures decreases as the pressure of the Ar carrier gas used in the supersonic expansion is increased, but the spin–orbit population ratios and the lambda-doublet preference is essentially the same under all the expansion conditions studied. The experimental observations are consistent with dissociation from a 1A′ excited state and the rotational energy of the OH fragment originating partially from the zero-point bending motion of the HOCl and partially from the parent rotational motion.