A new tool for reactionhyphen;path analysis of chemical dynamics is introduced, namely, series expansion of reactionhyphen;path potentials. This analysis involves the expansion of vibrational frequencies in powers of a reaction coordinate measuring progress along a suitably defined reaction path. The method is applied to generalizedhyphen;normalhyphen;mode vibrational frequencies along two choices of reaction path for the inversion of ammonia. The leading nonzero terms in the power series are calculated by Moslash;llerndash;Plesset secondhyphen;order perturbation theory and are fully converged with respect to basis set and the step size used for calculating the minimum energy path and the Hessian.
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