We present calculations of cross sections for one-and two-electron processes in collisions of H + , He 2+ , and C 6+with water molecules in the framework of the Franck-Condon approximation. We employ an independent-electron method and a classical trajectory Monte Carlo approach. Anisotropy effects related to the structure of the target are explicitly incorporated by using a three-center model potential to describe the electron-H 2 O + interaction. We derive scaling laws with respect to the projectile charge. We also estimate cross sections for molecular fragmentation subsequent to electron removal.

Multichannel quantum defect calculations for NO + dissociative recombination (DR) for electron energies from threshold to 8 eV are presented. The calculations use electronic energies and autoionization widths of valence states obtained from ab initio R-matrix calculations with the corresponding potential curves calibrated using available spectroscopic data. Six valence states open to dissociation are included in the final calculations. Excellent agreement with the measured cross sections is obtained for the low-energy DR, up to 3 eV and, for the first time, the peak observed in the cross section at high energy is accounted for. The importance of the various dissociative states at different electron energies, as well as the direct and indirect processes, is discussed. Compared to previous theoretical studies, the inclusion of a third dissociative state of 2 symmetry and the larger autoionization width of the B 2 state are found to be particularly important for the agreement with experiment.

A comprehensive theoretical study of NO Rydberg states and of Feshbach resonances associated with excited states of NO + is made for an internuclear separation of 2.175 a 0 . Calculations are performed using the UK R-matrix molecular package. The lowest four target states (X 1 + , a 3 + , b 3 and w 3 ) are considered in the construction of the CI target wavefunction. Quantum defect theory is employed to analyse the multiple Rydberg series obtained. In the bound-states region of the NO spectrum, six Rydberg series are resolved and quantum defects are given up to n = 11. In the continuum spectrum, Rydberg series of resonances converging to the three excited states of NO + considered are identified and compared with available experimental data. Some previous assignments for both bound and continuum states are reinterpreted and the dominant source of partial-wave mixing re-analysed. Data for the resonance widths are presented for the first time.

New coupled‐state R‐matrix calculations are performed at energies up to 1 eV to give rotational excitation and de‐excitation cross‐sections for electron collisions with CH+. Rotational excitations with Δ j up to 7 are considered. Transitions with Δ j up to 6 are found to have appreciable cross‐sections, those with Δ j = 2 being comparable to (indeed slightly larger than) those with Δ j = 1, the only ones considered previously. Rates for electron temperatures up to 15 000 K and critical electron densities are given. A model of CH+ rotational populations shows them to be relatively insensitive to electron temperatures in the range 800–2000 K, but to depend strongly upon electron density. The models predict a significant population in rotational states with j > 1 even at low electron densities; at higher densities the possibility exists that electron collisions alone might explain the recently observed populations in the planetary nebula NGC 7027.