Franck-Condon analysis of predissociations in the lower valence states of the NH radical

The origins of the predissociations observed by Smith, Brzozowski, and Erman for the A³Πand c¹Π states of NH have been investigated via a Franck-Condon analysis. It is shown that the measured variation of the predissociation probability is is proportional to the Franck-Condon densities between the bound rotational levels of the A and c states and the vibrational continuum of a ⁵Σ^- state arising from the ground state asympote. Similar calculations for the X³Σ^- ground state vibrational continuum, the only other state with a lower dissociation limit, showed that state to be ineffective in producing the observed predissociation.