VALIDATION OF TRAJECTORY SURFACE HOPPING METHODS AGAINST ACCURATE QUANTUM-MECHANICAL DYNAMICS AND SEMICLASSICAL ANALYSIS OF ELECTRONIC-TO-VIBRATIONAL ENERGY-TRANSFER

The validity of the quasiclassical trajectory surface hopping method i s tested by comparison against accurate quantum dynamics calculations. Two versions of the method, one including electronic coherence betwee n hops and one neglecting this effect, are applied to the electronical ly nonadiabatic quenching processes Na(3p) + H-2(nu = 0, j= 0 or 2) -- > Na(3s) + H-2(nu',j'). They are found to agree well, not only for que nching probabilities and final-state distributions, but also for colli sion lifetimes and hopping statistics, demonstrating that electronic c oherence is not important for this system. In general the accurate qua ntum dynamical calculations and both semiclassical surface hopping mod els agree well on the average, which lends credence to applications of semiclassical methods to provide insight into the mechanistic details of photochemical processes proceeding on coupled potential surfaces. In the second part of the paper the intimate details of the trajectori es are analyzed to provide such insight for the present electronic-to- vibrational energy transfer process. (C) 1997 American Institute of Ph ysics.