Vibrational predissociation of a rotating collinear triatomic model molecule.

Conventional quantum mechanical studies of molecular vibrations usually neglect the effects of rotation. When a rotating molecule has high enough energy to dissociate, this approximation is generally inaccurate. In this study, the effect of molecular rotation on vibrational predissociation is investigated for a model collinear H–C–C molecule. The vibrational–rotational interaction in this simple model is solely centrifugal, which introduces additional coupling of the two stretching modes. For a large range of angular momenta J, vibrational predissociation resonance widths (which are proportional to unimolecular state-specific reaction rates) are computed quantum mechanically using the complex coordinate method. The resonance widths are found to have substantial dependence on J. The results of corresponding classical trajectory studies show that the J-dependence of the resonance widths is a purely quantum effect. The quantum results are verified by a comparison of the complex coordinate method with the R-matrix propagation method. The resonance widths given by the two procedures are found to be in very good agreement. [ABSTRACT FROM AUTHOR]