Communication: Rotational excitation of interstellar heavy water by hydrogen molecules
Résumé
Cross sections and rate coefficients for low lying rotational transitions in D2O induced by para-H-2 collisions are presented for the first time. Calculations have been performed at the close-coupling level with the deuterated variant of the H2O-H-2 interaction potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)]. Rate coefficients are presented for temperatures between 1 and 30 K and are compared to the corresponding rate coefficients for H2O. Significant differences caused by the isotopic substitution are observed and are attributed to both kinematics and intramolecular geometry effects. Astrophysical implications are briefly discussed in view of the very recent detection of D2O by the Herschel Space Observatory.