Ortho-para-H-2 conversion by hydrogen exchange: Comparison of theory and experiment

International audienceWe report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional (de) excitation of H-2 by H. Our calculations are based on the H-3 global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. The reactive hydrogen exchange channels are taken into account. We show that the ortho-para and para-ortho conversion of H-2 are significant processes at temperatures above similar to 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-H-2 conversion by hydrogen exchange in astrophysics is discussed