Nonstationary time-series analysis of many-body dynamics

A method for the analysis of computer simulations of ultrafast dynamical processes in many-body systems is presented, based on a joint time-frequency Wigner-Ville distribution calculated from the evolving particle velocities. This quantity has the interpretation of a time- and frequency-dependent effective temperature, and the evolution of the distribution allows dynamical information about energy flow between modes and relaxation mechanisms of many-body systems to be obtained. This approach is illustrated for the example of vibrational relaxation of an ${\mathrm{I}}_2$ impurity in an argon cluster.