Electron-impact excitation from the ground and the metastable levels of Ar I

Electron-impact excitation of ArI from the ground 3p⁶¹S₀ as well as the two metastable levels of the 3p⁵4s (³P₂ and ³P₀) configuration to all ten levels of the 3p⁵4p excited configuration are calculated in the distorted-wave approximation. Polarization of the ground state is explicitly included by adding a polarization potential in the calculation. Unitarization of the scattering matrix S is carried out by including the elastic terms, and effects of unitarization in the LS as well as jj formalisms are investigated. The excitation cross sections are calculated from threshold to ~100 eV. The calculations are compared and contrasted with recent experimental data and other theoretical work. The study shows that the effect of the polarization potential is not very significant but unitarization of the S matrix reduces the cross sections considerably and the cross sections obtained using the two different methods of unitarization are significantly different for some excitation transitions. The results are useful for analyzing low-pressure plasmas used in processing applications as well as electron beam excitation, as in excimer lasers.