A quenching method in mixed quantum-classical dynamics calculations on nonadiabatic problems

A quenching method [Chem. Phys. Let. 262, 284 (1996)] is extended to study nonadiabatic reactive scattering within a mixed quantum-classical molecular dynamics simulation based on the time dependent self-consistent field. The quenching method is more straightforward for nonadiabatic reactive scattering than for the adiabatic case. A rigorous diabatic-adiabatic transformation for nonadiabatic problems is presented. It provides a theoretical basis for decoupling the bifurcating wavepacket in adiabatic reactive scattering and a new decoupling technique. The derivation illustrates clearly that a diabatic representation is convenient for both adiabatic and nonadiabatic reactive scattering within the mixed quantum-classical formulation. Two model examples are used to demonstrate the advantages of the quenching method for nonadiabatic reactive scattering. A comparison with the full quantum treatment is also made. (C) 1998 American Institute of Physics.