Mode-Specific Quasiclassical Dynamics of the F + CHI S2 and Proton-Transfer Reactions.

Mode-specific quasiclassical trajectory computations are performed for the F + CHI( v = 0, 1) S2 and proton-transfer reactions at nine different collision energies in the range of 1.0-35.3 kcal/mol using a full-dimensional high-level ab initio analytical potential energy surface with ground-state and excited CI stretching ( v), CH rocking ( v), CH umbrella ( v), CH deformation ( v), CH symmetric stretching ( v), and CH asymmetric stretching ( v) initial vibrational modes. Millions of trajectories provide statistically definitive mode-specific cross sections, opacity functions, scattering angle distributions, and product internal energy distributions. The excitation functions reveal slight vibrational S2 inversion inhibition/enhancement at low/high collision energies ( E), whereas large decaying-with- E vibrational enhancement effects for the S2 retention (double inversion) and proton-transfer channels. The most efficient vibrational enhancement is found by exciting the CI stretching (high E) for S2 inversion and the CH stretching modes (low E) for double inversion and proton transfer. Mode-specific effects do not show up in the scattering angle distributions and do blue-shift the hot/cold S2/proton-transfer product internal energies.