2013ApJ...765...77Y

Theoretical rotational quenching cross sections and rate coefficients of ortho- and para-H₂ O due to collisions with He atoms are presented. The complete angular momentum close-coupling approach as well as the coupled-states approximation for the angular momentum decoupling was applied to solve the scattering problem for a large range of rotationally excited states of water.
Result. are obtained for quenching from initial levels 1_1, 0_, 2_1, 2_, 2_2, 1_, 3_0, 3_, 3_1, 2_, 3_2, 1_, 4_1, 4_, 3_3, 0_, and 4_2, 3_ of ortho-H₂O and from initial levels 1_1, 1_, 2_0, 2_, 2_1, 1_, 2_2, 0_, 3_1, 3_, 3_2, 2_, 4_0, 4_, 4_1, 3_, and 3_3, 1_ of para-H₂O for kinetic energies from 10^–5 to 10⁴/cm. State-to-state and total deexcitation cross sections and rate coefficients for temperatures between 0.1 and 3000 K are reported. The present state-to-state rate coefficients are found to be in good agreement with previous results obtained by Green and coworkers at high temperatures, but significant discrepancies are obtained at lower temperatures likely due to differences in the adopted potential energy surfaces. Astrophysical applications of the current rate coefficients are briefly discussed.