Collisional excitation of H2O by H-2 molecules

Using accurate theoretical rigid-rotor interaction potential for H2O-H-2 and accurate coupled channel molecular scattering calculations, rates have been obtained for excitation of para- and ortho-H2O out of the lowest, j = 0, 1, and 2, rotational levels owing to collisions with para- and ortho-H-2 at kinetic temperatures from 20 to 140 It. Excitation by para-H-2 is not too different from excitation by He atoms, with most rates being within a factor of 1-3 larger, but excitation by ortho-H-2 is significantly different, with some rates an order of magnitude larger than rates for excitation by He atoms.