Spectroscopic study of vibrational excited CO self-relaxation and collisional relaxation

Abstract The collisional energy transfer in the pure CO and CO + CO 2 gas mixture systems was investigated by exciting CO X 1 Σ + (0, 7) to the vibrational excited-state CO X 1 Σ + ( V = 2, J = 8) using the stimulated Raman scattering technique. The Boltzmann distribution and the coherent anti-Stokes Raman scattering technique were utilized to obtain the population and lifetime τ of CO in two systems. The Stern–Volmer equation was used to fit the data to obtain the collisional energy transfer rate coefficients of the pure CO and CO + CO 2 gas mixture system. The collisional energy transfer rate coefficients of the pure CO system are greater than those of the CO + CO 2 gas mixture system, and the rate coefficients of both systems increase with temperature. The instantaneous laser-induced fluorescence spectra of CO(2, 8) were measured before and after collision with CO 2 in the gas mixture system, with the rate equations yielding the appearance and depletion rate coefficients of J in the rotational states of CO 2 (00 0 0). The depletion rate coefficients are an order of magnitude larger than the appearance rate coefficients in the low rotational state. Different rotational temperatures T r were obtained from the Boltzmann distributions of CO 2 (00 0 1, J ) and CO 2 (00 0 0, J ), with the rotational temperature of CO 2 (00 0 1, J ) being close to the heat-pipe oven temperature and that of CO 2 (00 0 0, J ) being higher than the heat-pipe oven temperature by a factor of ∼2, indicating that the vibrational energy of CO is transferred to the rotational energy of CO 2 .