THE INFLUENCE OF BARRIER TOPOGRAPHY ON THE DYNAMICS OF THE H-2 REACTION(F)

Classical trajectory calculations on a series of three DIM potential e nergy surfaces and a standard LEPS surface for the reaction H + F-2 -- > HF + F are reported. All surfaces have the same features in collinea r configurations but differ in the position, height and number of acce ssible saddle points in bent configurations. The dependence of reactio n cross sections, product energy and angular distributions, thermal ra te data and reaction mechanism on these features is investigated and d iscussed. The non-collinear part of the surfaces is of particular inte rest when it allows for microscopic branching, the various ensuing rea ction mechanisms making different contributions to the product propert y distributions. In particular, a broadening of the HF vibrational dis tribution together with the appearance of a component extending to ver y low vibrational levels can arise from reactive encounters passing th rough a T-shaped transition state.