Efficiencies of additives in the transfer of vibrational energy in ethylene and nitrous oxide

Abstract

Using ethylene or nitrous oxide as test molecules which contain different atoms and exhibit different internal modes of motion, measurements of the dispersion of ultrasonic velocities have been used to obtain information about vibrational energy transfer in the pure gases, and with a number of polyatomic molecules as additives. Much more efficient transfer is found with many of these additives than in self collisions. Even molecules such as benzene which are relatively inefficient in self collisions are good energy transfer catalysts in hetero-collisions. Mechanisms of energy transfer additional to the ‘high velocity impacts’ of Landau & Teller are discussed. In hetero-collisions with polyatomic molecules, vibration-vibration transfers offer one possibility. Wrestling collisions or profound perturbations of the energy levels of the vibrators by dipole fields also appear to be important.