Spectroscopic study of energy transfer in collisions between vibrational excited H2 and CO2.

The collisional energy transfer between vibrational excited H2(1, 7) and CO2 was investigated by exciting H2 to a vibrational excited state of v = 1, J = 7 by the stimulated Raman scattering technique. The coherent anti-Stokes Raman spectroscopy (CARS) technique determined that H2 was excited to the H2(1, 7) state. Varying the cuvette temperature, the number of H2(1, 7) particles was found to increase with the increase in H2 molar ratio α by scanning the intensity of the CARS spectrum, with peaks at different α at a temperature of 363 ± 15 K, but the peak temperature was not sensitive to α. Scanning CARS spectra after H2 collisions yielded that the energies of the excited states of H2 were mainly distributed in the vibrational and translational states, proving that the collisions between the excited states of H2 were linear collisions. The collisional transfer rate coefficients of H2(1, 7) and CO2 were obtained by fitting the Stern-Volmer equation as kv(H2) = (2.89 ± 0.30) × 10-13 cm3 s-1 and kv(CO2) = (8.23 ± 0.42) × 10-13 cm3 s-1. Exciting H2 to different states, it was found that the collisional transfer rate coefficient of CO2 was less affected by the energy of the vibrational excited H2. The rotational temperature was obtained from the Boltzmann distribution of the rotational dynamics, and it was found that the rotational temperature of CO2(0000, J) was about 3.4 times higher than that of CO2(0001, J), which proved that the energy of the vibrational excited H2 was mainly allocated to the higher rotational state of CO2(0000).