Experimental Investigations of Vibration–Vibration Energy Transfer in HBr(X 1 Σ + v '' = 5, 6)–H 2 Collisions

This study experientally investigated the vibration–vibration ( V – V ) energy transfer process in the HBr–H 2 mixing system (molar ratio: 0.4; total pressure: 500 Pa) at room temperature ( T = 295 K). Degenerate stimulated hyper-Raman pumping was used to excite HBr molecules to the X 1 Σ + v ′′ = 5, 6 excited states, and the population distribution of the ro-vibrational states of the H 2 molecules following collision was determined by coherent anti-stokes raman scattering (CARS) Spectroscopy. The scanning coherent anti-stokes raman scattering (CARS) spectra revealed that the H 2 molecules were populated at vibrational rotation energy levels of v = 1, 2 after colliding with the HBr ( v ′′ = 5, 6). The ratio of the population of each vibrational rotation energy level of the H 2 molecules was obtained through simple dynamic model analysis and the relative intensity ratio of the coherent anti-stokes raman scattering (CARS) spectrum. The analysis of the Boltzmann distribution and relative intensity ratio of the H 2 molecule v = 0 in thermal equilibrium demonstrated the population of the v = 1, 2 vibrational rotation energy level after the collision of the H 2 molecule with HBr ( v ′′ = 5, 6). After colliding with HBr ( v ′′ = 6), the ratio of the number of particles of the H 2 (1, 3) and (2, 3) levels ξ = n 1 / n 2 had multiple values, and the theoretical formula was fitted by the time-resolved coherent anti-stokes raman scattering (CARS) spectral profile. The actual population ratio was 1.76. The time evolution profile of the population number on the vibrational excited HBr ( v ′′ ≤ 5, 6) after colliding with the H 2 molecules was measured, and two-quantum near resonance in the HBr ( v ′′ = 5, 6) + H 2 system was observed. Thus, direct evidence that the two-quantum relaxation process occurred was provided.