Rate coefficients for electron-impact rotational excitation of H+3 and H3O+

Molecular <b><sansserif>R</sansserif></b>-matrix calculations are performed to obtain rotational excitation rate coefficients for electron collisions with the symmetric-top ions H⁺₃ and H₃O⁺ up to electron temperatures of 10000 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 H⁺₃ and populate the rotational levels of H₃O⁺ up to the (4, 1) level.