Electron-collisions with molecules of interstellar and plasma interest via the R-Matrix method

Here the ab-initio R-Matrix method has been used to carry out electron-molecule collision calculations on the the molecules of interstellar interest C3N, C2H & CN, and molecules found in industrial plasma applications SiBr, SiBr2 and NaI. These were carried out using the UK Molecular R-Matrix codes, along with the Quantemol expert system for running these codes. Calculations have also been carried out on electron collisions with atomic oxygen using these codes, with details included about the problems faced in running an atomic calculation with the molecular codes. Calculations on each species include comparison of different models, including staticexchange and close-coupling models (with different size CAS tried), various basis sets, and for some species different initial orbitals. These different initial orbitals were either taken from the codes themselves (for SCF orbitals), or the quantum chemistry program MOLPRO (for natural orbitals), for the latter numerous state averaged orbitals were tried with different weightings in order to produce good target energies for carrying into the scattering calculation. Results for all calculations include scattering observables such as eigenphase sums, elastic and excitation cross-sections, bound anionic states and resonance positions and widths. Also a new theory has been developed for calculating rotational cross-sections which includes the spin angular momentum of the incoming scattering electron, this has been implemented into the already existing code ROTLIN, which can calculate rotational cross-sections using the scattering data from an R-Matrix calculation.