Collisional excitation rates of H2O with H2 -: I.: Pure rotational excitation rates with para-H2 at very low temperature

Close coupling (CC) calculations of pure rotational excitation rates of H2O by para-H-2 are performed between 5 K and 20 K. Some discrepancies with Phillips et al. (1995, 1996) are found and explained. We find that the presence of resonances greatly influences the excitation rates at very low temperature. Fits of our collisional rates are provided.