Vibrational relaxation rates via equilibrium simulation of fluids: thermal softening

In this paper we report the results of one‐dimensional simulations of vibrational relaxation in a dense classical molecular fluid. The novel feature of the simulations is that we collect statistics on the energy transfer from vibrational to translational modes in individual collisions, instead of just monitoring the total vibrational energy of the system. This gives much more information on the microscopic processes involved, and in particular reveals that under a wide range of conditions the vibrational relaxation rate is dominated by an effect which we refer to as ‘‘thermal softening’’ of the vibration frequency. This effect is very important in defining and calculating the vibrational relaxation rate.