Absorption spectra for collinear (nonreactive) H3: Comparison between quantal and classical calculations

Absorption spectra for the collinear (nonreactive) H+H2→H♯3 →H+H2 are calculated quantum mechanically, using the Siegbahn–Liu–Truhlar–Horowitz (SLTH) ab initio potential and a model H*3 surface as the ground and excited H3 surface, respectively. They are compared to classical spectra previously computed by Mayne, Poirier, and Polanyi using the same potential energy surfaces [J. Chem. Phys. 80, 4025 (1984)]. The spectra are calculated at several collision energies and for both H+H2 (v=0) and H+H2 (v=1). The quantal and classical spectra are shown to agree with respect to basic features and trends. Nevertheless, the two sets of spectra differ considerably in their overall appearance because of some purely quantum aspects of the H+H2 system.