Ab initio investigation of the photofragmentation of bromomethanol

Abstract

Ab initio multi-reference configuration interaction calculations are carried out for ground and excited states of bromomethanol BrCH 2OH to investigate photofragmentation processes relevant to atmospheric chemistry. Five low-lying excited states with vertical excitation energies between 5.8 and 7.4 eV ( 1 1 A″, 1 3 A″, 2 1 A ′, 1 3 A ′, 2 3 A ′ ) are found to be highly repulsive for C–Br elongation leading to CH 2OH(X 2A ′) and Br (X 2P). Photodissociation along the C–O bond leading to BrCH 2 (X 2B 2) and OH (X 2Π) has to overcome a barrier of about 0.6–0.7 eV because the low-lying excited states 1 1 A″, 1 3 A ′ and 1 3 A″ become repulsive only after the C–O bond is elongated by about 0.2 Å.