R-matrix calculations for polyatomic molecular ions:: electron scattering by H3+ and H3O+

Electron impact calculations are presented for H-3(+) and H3O+ at their equilibrium geometry using coupled states expansions. The R-matrix method is employed as it is very efficient for characterizing the many resonances found in electronion collisions. Positions, widths and symmetries are obtained for the lowest ten Feshbach resonances for each ion. These resonances are important for explaining features observed in dissociative recombination experiments at energies of 5-10 eV. In addition a broad shape resonance at about 4.5 eV is identified for H3O+. Electronic excitation cross sections are obtained in reasonable agreement with recent storage ring experiments.