Electron-impact excitation of carbon and silicon in the distorted-wave approximation

The ${}_{}{}^3{}_{}{}^{}P\to {}_{}{}^1{}_{}{}^{}D$ electron-impact excitation cross section within the ground configuration of both neutral carbon and silicon is calculated in the distorted-wave approximation of the two-state Hartree-Fock coupled equations. An essential element of the present treatment is that we do not assume orthogonality to core orbitals in deriving equations for the scattering orbitals. A local adiabatic polarization potential is also added to the distorted-wave equations. Both elements are necessary in getting good agreement with close-coupling results for carbon to low impacting energies. The agreement is sufficiently good that our predictions for silicon should be accurate to within a factor of 2.