Role of intersystem crossing in the reactive scattering of O( 3P) atoms with CH 2I 2 molecules

Abstract

Reactive scattering of O( ³P) atoms with CH ₂I ₂ molecules has been measured at initial translational energies E˜48 and 15 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 both initial translational energies the angular distribution of IO scattering is mildly forward and backward peaked, slightly favouring the backward direction. Both product translational energy distributions peak at low energy with a long tail extending out to higher energy. Comparison with the predictions of phase space theory indicates that the IO product scattering arises mainly from long-lived collision complex dynamics following intersystem crossing from the initial triplet to the underlying singlet potential-energy surface, while a small contribution also arises from direct dynamics in IO scattering over a wide angular range with higher product translational energy. This pattern of behaviour is related to the structures of the reaction intermediates on both the singlet and triplet potential-energy surfaces.