Spectroscopy of the transition state (theory). II. Absorption by H‡3 in H+H2→H‡3→H2+H

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Abstract
Absorption spectra of transition state configurations in the reaction H+H2→H‡3 →H2+H have been computed. The density of H‡3 in configuration space was obtained from a classical trajectory study of collinear reaction on the Siegbahn, Liu, Truhlar, and Horowitz (SLTH) ab initio potential energy surface (PES). Vertical transitions were assumed to an upper PES H*3 modeled on limited ab initio data; four different model PES for H*3 were examined. The effects of varying reagent collision energy, varying reagent vibrational excitation, varying isotopic mass, and varying optical transition moment were explored. Transition state spectra were also computed for thermal distributions of H+H2, at 300 and 1000 K. The transition state spectra obtained constituted a wing extending as far as 40 000 cm−1 to the ‘‘red’’ of the Lyman‐α transition. As illustrated here, the wing exhibited features that reflected the dynamics of reaction on the SLTH PES.