Vibrational energy transfer in the N2*-OCS system. Measurements of vibrational populations of the bending manifold in the perturbed steady state by microwave spectroscopy

Microwave spectroscopy has been used to measure vibrational populations of various states of OCS in mixtures with excited nitrogen, obtained by continuously flowing the gases through an interferometric absorption cell. The perturbed steady state population of all the bending sublevels from nu-2 = 1 to 4 and of the (00(0)1) level in several different conditions of flow rate, total pressure, and partial pressures have been obtained. The results show that within the (3-nu-2) and (4-nu-2) bending levels the perturbed population of the sublevels is higher at higher energy. Moreover, in certain conditions a population inversion between the (04(0)0) and the (03(1)0) levels is observed. The present results are discussed in terms of a model which includes all the sublevels of the bending manifold up to nu-2 = 4, with and without a dipole-dipole interaction propensity rule. Only a qualitative accord with the experimental data is obtained.