Spectroscopic Study of Vibrational Excited CO Self-Relaxation and Collisional Relaxation

The collisional energy transfer in the pure CO and CO+CO2 gas mixture systems was investigated by exciting CO X1Σ+ (0, 7) to the vibrational excited-state CO X1Σ+ (V = 2, J = 8) using the stimulated Raman scattering (SRS) technique. The Boltzmann distribution and the coherent anti-Stokes Raman scattering (CARS) 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+CO2 gas mixture system. The collisional energy transfer rate coefficients of the pure CO system are greater than those of the CO+CO2 gas mixture system, and the rate coefficients of both systems increase with temperature. The instantaneous laser-induced fluorescence (LIF) spectra of CO(2, 8) were measured before and after collision with CO2 in the gas mixture system, with the rate equations yielding the appearance and depletion rate coefficients of J in the rotational states of CO2(0000). The depletion rate coefficients are an order of magnitude larger than the appearance rate coefficients in the low rotational state. Different rotational temperatures Tr were obtained from the Boltzmann distributions of CO2(0001, J) and CO2(0000, J), with the rotational temperature of CO2(0001, J) being close to the heat-pipe oven temperature and that of CO2(0000, 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 CO2.