Influence of a new potential energy surface on the rotational (de)excitation of H2O by H2 at low temperature

M.-L. Dubernet , F. Daniel , A. Grosjean , A. Faure (1) , P. Valiron (1) , M. Wernli (1) , L. Wiesenfeld (1) , C. Rist (1) , J. Noga , J. Tennyson

1 LAOG - Laboratoire d'Astrophysique de Grenoble

Aims.Using a newly determined 5D potential energy surface for H2-H2O we provide an extended and revised set of rate coefficients for de-excitation of the lowest 10 para- and 10 ortho- rotational levels of H2O by collisions with para-(j=0) and ortho-H2(j=1), for kinetic temperatures from 5 K to 20 K. Methods: .Our close coupling scattering calculations involve a slightly improved set of coupled channels with respect to previous calculations. In addition, we discuss the influence of several features of this new 5D interaction on the rotational excitation cross sections. Results: . The new interaction potential leads to significantly different rate coefficients for collisions with para-H2 (j=0). In particular the de-excitation rate coefficient for the 110 to 101 transition is increased by up to 300% at 5 K. At 20 K this increase is 75%. Rate coefficients for collisions with ortho-H2(j=1) are modified to a lesser extent, by up to 40%. The influence of the new potential on collisions with both para-(j=0) and ortho-H2(j=1) is expected to become less pronounced at higher temperatures.

M.-L. Dubernet, F. Daniel, A. Grosjean, A. Faure, P. Valiron, et al.. Influence of a new potential energy surface on the rotational (de)excitation of H2O by H2 at low temperature. Astronomy and Astrophysics - A&A, 2006, 460, pp.323. ⟨10.1051/0004-6361:20065804⟩. ⟨hal-00398287⟩