Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(3P) + CH2ICl Reaction

Abstract

Reactive scattering of O(3P) atoms with CH2ICl molecules has been measured at initial translational energies E ∼ 46 and 17 kJ mol-1 using a supersonic beam of O atoms seeded in He and Ne buffer gases generated from a high-pressure microwave discharge source. At the higher initial translational energy, the IO product scattering can be resolved into two components; one showing forward and backward peaking with a product translational energy distribution peaking at low energy with a tail extending out to higher energy, and the other that peaks in the backward direction with higher product translational energy. At lower initial translational energy, the IO product scattering does not allow the resolution of two components but peaks in the backward direction with a higher product translational energy than for scattering in the forward hemisphere. The slow component is attributed to dissociation of a long-lived OICH2Cl complex formed by intersystem crossing from the initial triplet 3A‘‘ potential energy surface to the underlying singlet 1A‘ potential energy surface. The fast component is attributed to direct reaction over the triplet potential energy surface with the sharp backward peaking arising from reaction on the 3Π2 and 3Π1 spin multiplet surfaces in near collinear OICH2Cl configurations and the scattering in the sideways and forward directions arising from reaction on the 3A‘‘ Renner Teller surface in strongly bent configurations. The contribution of the slow component is approximately one-third that of the fast component to the total reaction cross section for IO product scattering.