Vibrational quantization of polyatomic molecules. II

For pt.I see Mol. Phys., vol.31, no.1, p.97 (1976). The semiclassical quantization method of Einstein (1917), Brillouin (1926) and Keller (1958) is applied to some model Hamiltonians of two degrees of freedom which simulate non-separable molecular vibrations. A numerical scheme is based on the variation principle for invariant toroids and is used to obtain the regular energy spectrum over a wide range of energies. The scheme is rapid and effective, being about a factor v max 2N /(N 2 16 N 2+1/) faster than matrix diagonalization methods, where v max is a typical maximum vibrational quantum number and N is the number of degrees of freedom.