Statistical model for nonadiabatic decay of an exciplex strongly coupled to a dissociative continuum

We present a statistical model for the decay of an exciplex that is strongly coupled to repulsive ground-state potential energy surface. The motion of the exciplex is assumed to be governed by the excited electronic state adiabatic potential surface, and transitions to the ground state are caused by nonadiabatic transitions at a seam of avoided crossing of two strongly coupled diabatic states underlying the adiabatic representation. The model assumes that motion in the exciplex is ergodic. The predictions of the model are tested against accurate quantum dynamics and trajectory surface hopping calculations for Na*+H2→NaH2*→Na+H2.