El. Sibert et Ab. Mccoy, QUANTUM, SEMICLASSICAL AND CLASSICAL DYNAMICS OF THE BENDING MODES OFACETYLENE, The Journal of chemical physics, 105(2), 1996, pp. 469-478
The dynamics and spectroscopy of an adiabatic Hamiltonian, derived by
McCoy and Sibert [J. Chem. Phys. 105, 459 (1996)], describing the bend
ing motions of acetylene are presented and discussed. The resulting ei
genfunctions of this model are interpreted using classical, semiclassi
cal, and quantum mechanical descriptions of the vibrations. Using pert
urbation theory, the Hamiltonian describing the bends is reduced to tw
o coupled hindered rotor Hamiltonians. This simple Hamiltonian predict
s that local mode dynamics of the bending motion first occurs at about
6000 cm(-1) of excitation. This prediction is confirmed by the quantu
m mechanical studies. The hindered rotor Hamiltonian also predicts tha
t l-type doubling leads classically to stable periodic orbits correspo
nding to planar motion. The extent of planar type motion is quantified
using both semiclassical and quantum mechanical models. (C) 1996 Amer
ican Institute of Physics.