A potential function based on ab initio calculations has been developed for use in molecular dynamics (MD) simulations of the vibrational relaxation of L in xenon. The results from classical equilibrium and nonequilibrium MD simulations on the new potential suggest that the relaxation time, T-1, is more than 10 times longer than that obtained with previous potentials and is in good agreement with experimental results. Mechanistic information indicates that the relaxation mechanism is similar for both potential functions. A robust method for evaluating the Fourier transform of the force autocorrelation function is used to extract T, from the equilibrium MD simulations. (C) 2003 Elsevier B.V. All rights reserved.