Ab initio investigation of the photofragmentation of bromomethanol

Ab initio multi-reference configuration interaction calculations are carried out for ground and excited states of bromomethanol BrCH2OH to investigate photofragmentation processes relevant to atmospheric chemistry. Five low-lying excited states with vertical excitation energies between 5.8 and 7.4 eV (11A″, 13A″, 21A′, 13A′, 23A′) are found to be highly repulsive for C–Br elongation leading to CH2OH(X2A′) and Br (X2P). Photodissociation along the C–O bond leading to BrCH2 (X2B2) and OH (X2Π) has to overcome a barrier of about 0.6–0.7 eV because the low-lying excited states 11A″, 13A′ and 13A″ become repulsive only after the C–O bond is elongated by about 0.2 Å.