Dissociation dynamics of NH3(Ã1A ″2). Experiment and theory

Abstract

The spectroscopy and predissociation of the vibronic levels of the ùA″₂ excited states of NH₃ and ND₃ have been studied via Ã-X dispersed emission spectra, C′-à dispersed emission spectra and C′-à stimulated emission pumping, in each case following two-photon excitation to a selected intermediate level. The predissociation lifetimes span more than two orders of magnitude. The lowest levels predissociate by H(D) atom quantum tunnelling, the higher levels by vibrational rearrangement. A model calculation is presented to illustrate this mechanism for the v₁= 1 levels of the à state, which are very short-lived.