QUANTUM REACTIVE SCATTERING - DIABATIC APPROACH TO THE DYNAMICS OF CHEMICAL-REACTIONS

We present a diabatic approach to the dynamics of electronically adiab atic chemical reactions. A method is proposed for constructing diabati c surfaces from a single adiabatic potential surface. By using diabati c surfaces we can choose natural coordinate systems for both the react ant and product arrangements. The diabatic approach can be easily adap ted to exact quantum mechanical calculations based on variational scat tering formulations. The square integrable basis functions are obtaine d by diagonalizing the total Hamiltonian matrix which is constructed f rom the separate eigenfunctions on the reactant and product diabatic s urfaces. Applications to one-dimensional barrier problems and the coll inear H+H-2-->H-2+H reaction demonstrate the feasibility of the diabat ic approach. At low total energies, reaction probabilities for adiabat ic reactions can be reproduced by the present method. Moderately accur ate results can be obtained at high total energies for the collinear H +H-2-->H-2+H reaction, which may be improved by the optimal constructi on of diabatic surfaces.