Faure, Alexandre; Gorfinkiel, Jimena D. and Tennyson, Jonathan
Electron-impact rotational excitation of water.
Monthly Notices of the Royal Astronomical Society, 347(1),
Rotational excitation of H2O, HDO and D2O by thermal electron impact is studied using the molecular R-matrix method. Rate coefficients are obtained up to electron temperatures of 8000 K. De-excitation rates and critical electron densities are also given. It is shown that the dominant transitions are those for which DeltaJ = 0, +/-1, as predicted by the dipolar Born approximation. However, a pure Born treatment is found to overestimate the cross-sections close to threshold energies and to neglect important (dipole forbidden) transitions, owing to the importance of short-range and threshold effects. In the context of cometary water, the contribution of electron collisions might explain the need for large H2O-H2O collisional excitation rates in population models that neglect electrons.
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