RRKM theory beyond the separable harmonic approximation: The HCO2 -> H+CO2unimolecular decomposition

We report variational calculations of a large number of vibrational states of HCO2 and the H ... CO2 transition state for J = 0 using the code MULTIMO DE and a realistic six degree-of-freedom potential energy surface. State-de pendent rotational constants for both species are calculated for the same s ets of vibrational states from exact rotation/vibration calculations for J = 1. The results of these variational calculations are used to obtain RRKM rate constants for the decomposition of HCO2 to form H + CO2. Comparison is made between these nonseparable RRKM results and those obtained from a sta ndard, separable harmonic oscillator/rigid rotor evaluation of the RRKM rat e constant expression. Significant differences between the nonseparable and separable results are found.