State-to-state photodissociation of OCS (ν2=0,1|JlM). I. The angular recoil distribution of CO (X 1Σ+;v=0|J)

Abstract

State-to-state photodissociation experiments of OCS at 230 nm are reported using hexapole state selection of the parent molecule and velocity map ion imaging of the angular recoil of the CO photofragment. The role of the initial rovibrational state (ν2=0,1|JlM) of OCS on the angular recoil distribution is investigated. The CO (X 1Σ+;v=0|J) rotational distribution as well as the angular recoil anisotropy parameter β of the CO photofragment are reported for dissociation of single rovibrational (ν2=0,1|JlM) quantum states of OCS. A strong dependence of the anisotropy parameter β on the initial bending state, ν2=0 or 1, of OCS is observed. The effects of the initial bending state of OCS are rationalized in terms of the strong angular dependence of the transition dipole moment function of OCS for the 1 1Σ−(1 1A″) and 1 1Δ(2 1A′) excited state surfaces involved in the dissociation at 230 nm. The state-to-state imaging experiment provides a revised and improved determination of the binding energy of OCS (ν1,ν2,ν3=0,0,0|J=0)→CO (X 1Σ+;v=0|J=0)+S (1D2), D0=(4.284±0.009) eV.