Exciplex funnel resonances in chemical reaction dynamics: The nonadiabatic tunneling case associated with an avoided crossing at a saddle point

We report quantum mechanical calculations on a one-dimensional model of a chemical reaction with an electronically excited exciplex funnel over the saddle point to study the competition between direct reflection from the upper diabat and metastable trapping (resonances). Particular emphasis is placed on the effect of the funnel on transition probabilities and delay times as a function of energy and as a function of the magnitude of the energy gap at the saddle point. Quantum dynamics calculations of energy-dependent transition probabilities for a series of energy gaps reveal a regime where the main effect is diabatic reflectivity in direct, short-lived collisions and another regime where the main effect is a series of collisional resonances.