2 1S excitation of helium: A precise distorted wave approach

Abstract
The differential and total cross sections are evaluated for 1 1S–2 1S excitation of helium atom by electron impact in distorted wave approximation. The effect of the distortion of incident electron, contribution due to polarization of target and the exchange effect are appropriately taken in both the initial and final channels. Fourier decomposition of interaction potential between the projectile and target is taken and an accurate form factor has been used to calculate the transition matrix. The present results are compared with various distorted wave models as well as other theoretical and experimental results.