Role of intersystem crossing in the reactive scattering of O(3P)atoms with CF3CH2Imolecules
Abstract
Reactive scattering of O(3P) atoms with CF3CH2I molecules has been measured at initial translational energies Eā45 and 16 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 observed IO product scattering is found to be compatible with reaction via a long-lived collision complex. This is attributed to intersystem crossing from the initial triplet potential energy surface to the underlying singlet potential energy surface that supports a stable OICH2CF3 intermediate. However, the angular distribution of IO scattering at higher initial translational energy shows a mild preference for backward scattering, which is attributed to a small fraction of direct reaction dynamics over the triplet potential energy surface. No scattering of HOI reaction product is observed as this reaction pathway requires abstraction of a terminal H atom via a five-membered ring transition state and this is inhibited for the singlet OICH2CF3 intermediate by the fluorination of the terminal CF3 group.