ON THE IMPORTANCE OF HIGHER-ORDER ANHARMONIC MOLECULAR COUPLINGS

The dynamics of molecular vibrational dephasing (IVR) are governed by the coupling structure of the vibrational Hamiltonian. We use a recent ly developed factorization model for normal coordinate potentials to c ompare the importance of direct high order couplings to both direct lo w order couplings and low-order coupling chains. The importance of hig h order couplings is characterized as a function of the vibrational en ergy and of molecular size. Particular attention is paid to phase canc ellation effects in coupling chains, and to correlations between vibra tional modes depending on their localization length. To account proper ly for IVR at high densities of states and long times, high order coup lings must be taken into account. (C) 1998 American Institute of Physi cs.