Atom–diatom reactive scattering. I. Quantum theory

We describe a time-independent quantum theory for atom–diatom reactive scattering using a procedure based upon a division of configuration space into three distinct chemical channels. Within each chemical channel, coordinate systems defined as transformations of Jacobi coordinates are described which allow the use of R-matrix propagation in solving for the unbound motion along a scattering coordinate. The remaining five degrees of freedom are treated variationally, making use of the efficient discrete variable representation to describe the vibration–rotation interaction. The scattering information from the three chemical channels is matched on the common boundary, and the full S matrix is obtained at fixed total energy, angular momentum, and parity. In the second paper of this series, accurate results for the reactions of H+H2 and its isotopomers will be presented.