Energy Transfer in Classical Br2–Ar Collisions

Abstract

Computer calculations of three-dimensional classical trajectories for Br2–Ar collisions indicate that vibration-rotation coupling in the Br2 molecule can play a significant role in energy transfer. For Br2 molecules with specified initial internal energies embedded in a heat bath of Ar at 1800°K, probability distributions for internal energy changes and angular momentum transfers were determined. These indicate the possibility of attaining classical Br2 angular momenta large enough so that “vibrational energy” and “rotational energy” for the free molecule are not separable, and that collisions with large angular momentum changes may be responsible for a large part of the over-all Br2–Ar energy transfer. Amplitudes of vibration–rotation coupling are presented for Br2 energies of 0.1 De, 0.5 De, and 0.9 De, through a range of angular momentum found to be pertinent to the problem. Possible implications of the results for Br2–Ar energy transfer in shock-tube studies are discussed.