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 products of the proton transfer reaction O− + HF → OH + F− at center-of-mass collision energies of 45.0 and 55.8 kJ mol−l (0.47 and 0.58 eV, respectively). At both collision energies, the product angular distributions show forward–backward symmetry, characteristic of the decay of a transient complex living at least several rotational periods. The product kinetic energy distributions show structure that is clearly attributable 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 the rotational state distribution for that state. At the higher collision energy, the product kinetic energy distribution shows a clear angular dependence, from which we infer a transition to more direct dynamics involving low impact parameter collisions that access the repulsive wall of the potential surface in bent geometries. The vibrational energy 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 attribute 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 energy repulsive wall of the potential energy surface.