Rate coefficients for electron - impact rotational excitation of H + 3 and H 3 O +

Molecular R-matrix calculations are performed to obtain rotational excitation rate coefficients for electron collisions with the symmetric-top ions H3 and H3O + up to electron temperatures of 10 000 K. De-excitation rates and critical electron densities are also given. It is shown that short-range interactions, which are ignored in the standard Coulomb–Born theory, are crucial for studying electron-impact rotational excitation of molecular ions. In particular, our calculations show that electron collisions could help to create and maintain the predicted population inversion between the (J , K ) = (4, 4) and (3, 1) levels of H3 and populate the rotational levels of H3O+ up to the (4, 1) level.