Semiclassical vibrational energies and transition frequencies for a Hamiltonian with stretchndash;bend potential energy coupling: Application of Fourier methods

摘要

Semiclassical methods are applied to determine transition frequencies and vibrational energies for the twohyphen;mode HC2stretchndash;bend Hamiltonian recently studied by Swamy and Hase lsqb;J. Chem. Phys.84, 361 (1986)rsqb;. The mean action spectral approximation for calculating transition frequencies is found to give results in excellent agreement with quantum variational values. The FFT EBK method is used to calculate vibrational eigenvalues for both nonresonant and 3:1 resonant states. Both approaches give results more accurate than those reported by Swamy and Hase using the DeLeonndash;Hellerndash;Miller method. The presence of stretchndash;bend potential coupling is found to reduce the extent of classical chaos.