THE ENERGY RELAXATION OF A NONLINEAR OSCILLATOR COUPLED TO A LINEAR BATH

We develop an expression for the rate of energy relaxation of a nonlin ear oscillator coupled to a linear, dissipative bath. This particular type of model has wide applicability to studies of relaxation rates of vibrational modes in chemical systems. The energy relaxation rate is estimated by relating the anharmonic oscillator to an effective harmon ic reference system. The theoretical predictions compare favorably wit h simulation results for the energy relaxation of a Morse oscillator ( i) coupled to an Ohmic bath and (ii) coupled to a bath with exponentia lly decaying friction. The dependence of the initial relaxation rate o n the excitation energy of a Morse oscillator is qualitatively differe nt for the two cases. When the oscillator is coupled to an Ohmic bath, the initial relaxation rate decreases as a function of the excitation energy. When exponentially decaying friction is employed, however, th e initial relaxation rate is an increasing function of the excitation energy. (C) 1995 American Institute of Physics.