Electron collisions with the CN radical: bound states and resonances

CN is a fundamental molecule found in numerous environments and as such it is important to understand the processes in which it can be involved in. Its counterpart anion, CN-, was one of the first molecular anions to be detected in the interstellar medium (ISM). Ab initio electron-molecule scattering calculations for the neutral radical CN are presented. A number of target calculations are carried out to obtain a model which corresponds with experimental target data; these models test the use of different basis sets, and both Hartree-Fock and natural orbitals. A range of scattering models are considered, including static exchange and close-coupling methods. Results are presented for bound and resonance states of the anion, eigenphase sums, elastic cross-sections and electronic excitation cross-sections for electron scattering with the neutral radical. These results are subsequently analysed at a range of bond lengths. It is found that the electronic resonances are all too high in energy to be important for anion formation in the interstellar medium. Electron impact electronic excitation is considered to the A (2)Pi and B (2)Sigma(+) states, source of the 'CN red' and 'CN violet' electronic bands respectively.