STATE-TO-STATE MEASUREMENTS OF INTERNAL ROTATIONAL PREDISSOCIATION IN OH-AR (A(2)SIGMA(+))

Internal rotational predissociative levels of OH-Ar (A (2) Sigma(+)) have been identified lying up to 350 cm(-1) above the OH A (2) Sigma(+) (v = 0, 1)+Ar dissociation limit. The predissociative level energies, lifetimes, and OH A (2) Sigma(+) rotational product distributions have been measured. Complexes prepared in many of these predissociative levels are long lived with lifetimes greater than or equal to 50 ps. A novel variation of stimulated emission pumping has enabled quantitative OH A (2) Sigma(+) rotational distributions to be obtained following OH-Ar predissociation. The OH product distributions are highly selective. The highest energetically available channel is always populated, yet in many cases, low rotational levels are conspicuously absent. The OH-Ar predissociative levels have been assigned nearly good quantum numbers based on a rotational contour analysis of the predissociative features and/or the OH A (2) Sigma(+) rotational product distributions. A two-step mechanism involving Coriolis coupling and the potential anisotropy has been proposed to describe the predissociation process. A comparison between the experimentally measured and theoretically calculated observables provides a guide for further refinements of the OH A (2) Sigma(+) +Ar potential energy surface.