Classical dynamics of intramolecular energy flow in ethane

Abstract

Classical trajectory calculations on an ab initio potential surface are reported for the ethane molecule. Most calculations were performed for molecules possessing high rotational energy, with the initial conditions chosen to be consistent with rotational quantum numbers in the range J⩽ 280 and 0 ⩽K≲ 60. The initial energies were usually chosen to be above the dissociation limit for the process C₂H₆→ 2CH₃, and the conditions under which separation could occur, even when classically forbidden, were explored. During the trajectory, instantaneous values of the rotational quantum numbers, J, K, and of the vibrational angular momentum quantum number J(v), vary with time. These variations are small, but it is shown that they can be sufficient, at some energies, for the height of the centrifugal barrier to fall below the value of the total energy of the molecule, allowing it to dissociate when the initial conditions were such that it could not.