Energy transfer in reactive and nonreactive collisions of Na with Na 2

Abstract

Stimulated by the experimental finding of vibrationally and rotationally cold dimers in supersonic nozzle molecular beams of sodium, we have studied energy transfer in collisions of Na with Na 2 over a wide range of initial relative translation energies E and impact parameters b by a classical mechanical trajectory method. The vibrational and rotational energies were initialized using Boltzmann distributions characterized by temperatures T vib = 150 K, T rot = 50 K. We find that for large values of E the energy transfer in reactive collisions increases with b while it decreases with b for the nonreactive collisions. For low values of E, energy transfer is a decreasing function of b for both reactive and nonreactive encounters. Both the reactive and nonreactive mechanisms are very efficient in effecting transfer, between 40–70% of the initial relative translational energy is converted into internal energy of the diatom, leading to the conclusion that the reverse collisions would result in the rapid relaxation observed in experiment.