Ortho–para-H2 conversion by hydrogen exchange: Comparison of theory and experiment
Résumé
We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional (de)excitation of H2 by H. Our calculations are based on the H3 global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)10.1063/1.1432319]. The reactive hydrogen exchange channels are taken into account. We show that the ortho-para and para-ortho conversion of H2 are significant processes at temperatures above ∼300 K and for the last process we provide the first comparison with available experimental rate coefficients between 300 and 444 K. The good agreement between theory and experiment is a new illustration of our detailed understanding of the simplest chemical reaction. The importance of the ortho–para-H2 conversion by hydrogen exchange in astrophysics is discussed.