Direct dynamics study of energy transfer and collision-induced dissociation: Effects of impact energy, geometry, and reactant vibrational mode

Quasiclassical, direct dynamics trajectories, calculated at the B3LYP/6-31G** level of the theory, have been used to study the energy transfer dynamics and collision-induced dissociation ~CID! of formaldehyde cation in collisions with Ne. Effects of varying collision energy were probed for ground state H2CO , and H2CO 1 with excitation in three different vibrational modes: n6 1 ~in-plane CH2 rock!, n4 1 ~out-of-plane bend!, and n5 1 ~asym. CH stretch!. The trajectories are in excellent agreement with an earlier detailed experimental study of state-selected H2CO 1 CID. Energy disposal branching between product recoil, vibrational energy, and rotational excitation is found to vary with collision energy, vibrational state, impact parameter, and orientation. An analysis of the trajectories illustrates how mode-specific vibrational excitation effects the efficiency of translational-to-vibrational (T→V) energy transfer to promote CID. © 2003 American Institute of Physics. @DOI: 10.1063/1.1588634#