Quantum dynamics of overtone relaxation in benzene. V. CH(v=3) dynamics computed with a new ab initio force field

Large-scale quantum mechanical calculations of the CH(v=3) overtone spectrum and survival probability are reported for 21-mode planar benzene. A valence coordinate hybrid force field built from the following two sets of ab initio information was used: (1) the quartic DZP/SCF force field recently reported by Maslen et al.; (2) a force field computed at the 6-311G/MP2 level for the overtone excited CH chromophore. Comparisons are made between these results and the overtone spectrum and survival probability computed using the older Pulay et al. 4-21P/SCF scaled quadratic plus cubic force field. In addition, comparisons are made with experimental spectra from two research groups. These comparisons provide information about the sensitivity of the computed results to alterations in the input force field.