Low-energy electron collisions with atomic oxygen: R-matrix calculation with non-orthogonal orbitals

The low-energy electron collision with neutral oxygen has been investigated using a modified R-matrix method based on the B-spline representation of t he scattering orbitals, Integral cross sections for elastic scattering and for excitation of the P-3-D-1, P-3-S-1 and D-1-S-1 transitions are presente d in the energy region from threshold to 30 eV, Accurate representation of target wavefunctions has been obtained on the basis of the non-orthogonal o rbitals. Both the correlation and relaxation effects are shown to be import ant. The close-coupling expansion consists of the 26 spectroscopic bound an d autoionizing target states. A calculation with 26 spectroscopic states an d 17 pseudo-states has also been carried out to check the effect of couplin g to the continuum. The present results for the elastic scattering are in e xcellent agreement with the measurements, but large discrepancies with the existing experimental data are found for the P-3-D-1 and P-3-S-1 transition s. The excitation cross sections agree well with the recent R-matrix calcul ation with pseudo-states by Thomas et al (Thomas M R J, Bell K L and Berrin gton K A 1997 J. Phys. B: At. Mol. Opt. Phys. 30 4599) except: for lower en ergies about 5-7 eV of threshold.