Experimental Study of Rotational Relaxation in H2(1,9) Molecules Induced by Collisions with N2 and H2
摘要
The rotational relaxation of H2 (X1∑g, v = 1, J = 9) molecules during collisions with H2 and N2 was experimentally investigated. The rotational relaxation rate coefficient of H2(1,9) molecules was determined by fitting the Stern–Volmer equation. At 297 K, the self-relaxation rate coefficient for H2(1,9)–H2 collisions in a pure H2 system was (1.79 ± 0.04) × 10–14 cm3 s–1, while the rotational relaxation rate coefficients for H2(1,9) molecules colliding with H2 and N2 in a H2–N2 mixture were (0.74 ± 0.09) × 10–14 cm3 s –1 and (3.40 ± 0.21) × 10–14 cm3 s–1, respectively. The evolution profiles of the population distribution across various levels of H2 (v = 1, J ≤ 9) were measured in H2–N2 mixtures, providing experimental evidence for the multi-quantum relaxation of H2(1,9) molecules. Based on the analysis of the dynamic equations, it can be concluded that the primary pathway for multi-quantum relaxation of H2 with ΔJ = 4 is via rotational-rotational collisions between H2–H2. The self-relaxation rate coefficient of H2(1,9) molecules within a delay time of 2 μs was approximately 29% higher than that observed thereafter, indicating that rotational-rotational relaxation between H2 molecules occurs more rapidly than rotational-vibrational relaxation involving both H2 and N2. In the temperature range of 297–410 K, increasing temperature significantly enhances the rotational-vibrational relaxation of H2(1,9) with both H2 and N2, while the rotational-rotational collisions among H2 molecules exhibit small dependence on temperature.