The state-to-state photodissociation dynamics of HOD(Ã)

Abstract

HOD, rotationally state selected in the third and fourth OH stretching overtone (|04〉, |05〉) levels, has been photodissociated via the à state at λ≃ 288 nm. In accord with previous studies, H + OD is the dominant dissociation channel, with the yield of OH photofragments being below the detection limit in both sets of experiments. Model Franck-Condon calculations suggest that the OD photofragment rotational state distributions, determined by OD(A-X) laser induced fluorescence (LIF), reflect primarily the rotational and zero-point bending motions in the selected rovibrational state of HOD(X̃). However, in contrast to the state selected photodissociation of H2O, the OD rotational distributions from HOD also reveal the influence of a small exit channel torque, which is enhanced in the photodissociation of the deuterated molecule by the shift in the OD centre-of-mass relative to that in OH. A modified Franck-Condon model, which accounts approximately for this modest impulsive torque, qualitatively reproduces the observed behaviour.