Collisional excitation rates of H₂O with H₂

II. Rotational excitation with ortho-H₂ at very low temperature and application to cold molecular clouds

¹ Laboratoire d'Astrophysique, UMR CNRS 6091, Observatoire de Besançon, Université de Franche-Comté, 41 bis avenue de l'Observatoire, BP 1615, 25010 Besançon Cedex, France
² LERMA FRE 2460, Observatoire de Paris, Section de Meudon, 5 place Janssen, 92195 Meudon Cedex, France
³ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9, France

Corresponding author: M.-L. Dubernet, marie-lise.dubernet@obspm.fr

Received: 13 March 2003
Accepted: 12 June 2003

Abstract

We present the results of close coupling calculations of pure rotational excitation rate coefficients of H₂O by ortho-H₂, performed between 5 K and 20 K. At 20 K there is a good agreement with those results obtained previously by Phillips et al. (1996). Fits of our de-excitation collisional rate coefficients are provided. These new rate coefficients are used in the modelling of cold interstellar clouds to determine the influence of the precision of the rate coefficients on predicted line intensities.