Résumé
Cross sections and rate coefficients for low lying rotational transitions in HDO induced by para and ortho-H-2 collisions are presented for the first time. Calculations have been performed at the close-coupling and coupled-states levels with the deuterated variant of the H2O-H-2 interaction potential of Valiron et al. [J. Chem. Phys., 2008, 129, 134306]. Rate coefficients are presented for temperatures between 5 and 100 K and are compared to the corresponding rates for H2O and D2O. Significant differences caused by the isotopic substitution, in particular the C-2v symmetry breaking, are observed. Finally, our rates are found to be significantly larger (by up to three orders of magnitude at 50 K) than the corresponding HDO-He rates and should lead to a thorough re-estimation of the abundance of interstellar HDO.