Excitation Cross-section Evaluation for the Lowest Auto-Ionizing State of Potassium

The accuracy and reliability of any theoretical scattering model relies on the wave functions used and the energy of the projectile. Perturbation methods are known to be accurate at intermediate and high energies of the incident projectile but this accuracy also depend on the distortion potentials employed and the consideration given to higher order terms and the exchange effects. In a distorted wave model the initial state distorted wave is generated by the static potential of the target atom in the initial state and the final state distorted wave is generated by a potential taken as the sum of one-half of the initial state static potential and one half of the final state static potential of the target atom. We used this model to evaluate the integral and differential cross-sections as well as alignment and lambda parameters for electron-impact excitation of the lowest auto-ionizing states of K in the energy range of 18-1000 eV. The wave functions employed are the multi-zeta Hartree-Fock single electron wave functions. The numerical calculations are performed using DWBA1 program, which we modified to evaluate the exchange amplitudes exactly without any approximation. We have compared our results with other known theoretical and experimental results. From our alignment parameter results, we observed a near threshold resonant structure. (author)