The influence of parent rotation on the dissociation dynamics of the à 1 A″2 state of ammonia

Model calculations are presented to account for the observed rotational dependence of the dissociation of NH3 from the lower vibrational levels of the à 1 A″2 state. Centrifugal modification of, and Coriolis coupling between, vibrationally adiabatic surfaces highlights the dominant role of Coriolis coupling from all but the zero-point level on the dissociation rates which are controlled by quantum tunnelling. The distribution over NH2 product rotational states is explored by the use of quantum wavepackets propagated on the à and [Xtilde] potential energy surfaces which possess a conical intersection in the exit channel from the quasi-bound inner well of the à state. Coriolis coupling is again found to play an important role in determining the product distribution. In particular, it is predicted that there should be a significant orientation transfer if NH3 is dissociated using circularly polarized light via high J, low K rotational states of the 21 vibrational level of the à state.