The effect of bending vibrations on product rotations in the fully state-resolved photodissociation of the <i>A</i> state of water

Abstract

Theoretical calculations and experimental measurements determine the influence of initial bending vibration on the rotational states of the OH product following the photodissociation of water through its à state. Excitation from an initial state with no bending excitation reaches only a rather isotropic region of the excited state potential energy surface, but excitation from states with excited bending vibrations reaches more anisotropic regions. Close-coupling calculations that include the anisotropy of the Ã-state potential show that the torque exerted by the potential reduces the amount of rotational excitation below that predicted in the absence of anisotropy of the Ã-state potential. The experimental measurements for initial bending states having no, one, and two quanta of bending excitation, along with three or four quanta of stretching excitation, agree with the theoretical predictions. The measured product rotation increases with increasing bending excitation, and the observed rotational excitation is less than the limit for an isotropic potential.