Calculation of total cross sections for the scattering of slow electrons by heliium atom

First, we have calculated total cross-sections and momentum-transfer cross-sections for the scattering of slow electrons by helium atom by simple wave function .However, there is large discrepancy between the calculated results and experimental data at low energies less than 5ev .Hence a further study of the problem with more accurate wave function is quite necessary. By use of the more accurate wave function for helium atom we have derived the analytic potential function for the incident electron with the helium atom, including the exchange and polarization effects. With the partial wave method, we have further calculated the distorted wave functions, phase shifts, scattering cross-sections and momentum-transfer cross-sections for the slow electrons moving in the atomic field represented by the derived potential function. The numerical results for the scattering cross-sections and momentum-transfer cross-sections arc in good agreement with experiments. From the results of the present calculations, we know that both the polarization and exchange effects are very important for the incident electron with energy lower than 10 ev.The two effects would greatly be lower the cross-section for the slow electrons .Hence in the calculation of cross-sections for the scattering of slow electrons from atoms, both the polarization and exchange effects must be taken into account.