Vibrational energy exchanges between N2 and strongly excited CO molecules:: their role in vibrational kinetics

The rate constants for multiquantum vibration-to-vibration (V-V') energy exchanges in CO(v)-N-2(v') collisions, with CO in highly excited vibrational levels v and N-2 in the first few low-lying vibrational levels, were obtained from ab initio semiclassical calculations. A large temperature interval was explored, T = 100-500 K, while the vibrational quantum numbers v and v' were in the range v = (30-44) and v' = (0-3). The role played by these collisional processes in the vibrational kinetics of CO:Ar/He:N-2 gas mixtures under typical laser conditions were explored in detail by using a recently developed kinetic modelling procedure. In particular, it was found that the V-V' exchanges between CO and N-2 exert an essential influence on the time evolution of the vibrational population and on the associated small signal gain and spectral characteristics of the CO laser in both the fundamental and overtone bands.