Vibrational deactivation of N-2(v=1) by inelastic collisions with He-3 and He-4: An experimental and a theoretical study

A new N-2-He intermolecular potential with vibrational coordinate dependence is presented. Rate constants for the vibrational deactivation of N-2(v = 1) by He in the gas phase have been calculated over the temperature range 5-300 K, Accurate values of the rate constants for this process are known down to 100 K. We have now extended these measurements down to 70 K for the deactivation of N-14(2)(v = 1) by He-4 and down to 50 K for the deactivation of N-15(2)(v = 1) by He. Agreement between the theoretically calculated and the experimentally determined rate constants is excellent with the calculated values reproducing the experimental measurements within their error bars. An investigation of the low impact energy regime is also presented. While this focuses on collision energies of less than 20cm(-1) and yields rate constants which are in a temperature region inaccessible to our experimental method, it gives further insights into the influence of the attractive well on vibrational energy transfer processes. (C) 1997 American Institute of Physics.