PROTON-TRANSFER DYNAMICS ON HIGHLY ATTRACTIVE POTENTIAL-ENERGY SURFACES - INDUCED REPULSIVE ENERGY-RELEASE IN O-+HF AT HIGH COLLISION ENERGIES

We present the angular and kinetic energy distributions for the produc ts of the proton transfer reaction O- + HF --> OH + F- at center-of-ma ss collision energies of 45.0 and 55.8 kJ mol(-1) (0.47 and 0.58 eV, r espectively). At both collision energies, the product angular distribu tions show forward-backward symmetry, characteristic of the decay of a transient complex living at least several rotational periods. The pro duct kinetic energy distributions show structure that is clearly attri butable to the formation of OH in v' = 0, 1, and 2. The kinetic energy distribution for a single vibrational state of OH is equivalent to th e rotational state distribution for that state. At the higher collisio n energy, the product kinetic energy distribution shows a clear angula r dependence, from which we infer a transition to more direct dynamics involving low impact parameter collisions that access the repulsive w all of the potential surface in bent geometries. The vibrational energ y in the products decreases with increasing collision energy, with fv' , the fraction of available energy appearing in vibration, decreasing from 0.28 to 0.22 over the reported collision energy range. We attribu te this behavior to a transition from mixed energy release of a Heavy + Light-Heavy collision system dominated by the strong attractive well to induced repulsive energy release as the system reaches the low ene rgy repulsive wall of the potential energy surface.