Electron impact double excitation of (2S2) 1s and (2S2P) 1p states of helium atom using a distorted wave method

ABSTRACT

Cross section studies are important as they supply fundamental level researchers with necessary information and predictions for their experiments. Once experimental measurements agree with some prediction, the theoretical model yielding the prediction is then applied to other situations and finally validated. Very few studies have been made on electron impact double excitation of (2s2) 1S and (2s2p) 1P states of helium and even the results obtained in these studies do not agree among themselves. It is on this ground that the cross sections for the excitation of the above states have been calculated using a modified distorted wave method. In this method, a linear combination of the static potentials of the helium atom in the initial and final states is taken as the final channel distortion potential and the initial state static potential of the helium atom is taken as the initial channel distortion potential. Analytic wave functions for the ground and excited states are used. Numerical calculations are performed using a modified DWBA1 computer program. It is noticed that the effect of the exchange is appreciable up to about 400 eV for the (2s2) 1S excitation and up to 200 eV for (2s2p) 1P excitation. It is encouraging that the results obtained agree well with some of the theoretical and experimental data.