Influence of electron correlation on scattering cross-sections for He.

Total cross sections for high-energy inelastic collisions between helium atoms originally in their ground state have been obtained within the framework of the first Born approximation. The ground state of the helium atoms was described by the 35- configuration CI wavefunction of Weiss expressed in the form of a natural expansion, thereby facilitating an examination of the influence of ground state correlation effects on the scattering cross sections. Part II The natural expansion of the Weiss 35-configuration CI wavefunction for helium was used to assess the behaviour of high-energy electron-capture cross sections for the reaction H+ + He(1s2) ? H(nl) + He+(1s) when the target is described by wavefunctions of varying sophistication. The impulse approximation and the continuum distorted wave approximation were used to evaluate the above cross sections for proton impact energies ranging from 25 keV to 3.5 MeV. It was found that, in contrast with the impulse approximation, the continuum distorted wave (CDW) method is easily applied to electron capture reactions and overall gave the better agreement with experiment. The CDW method was also used to obtain capture cross sections for alpha particles impinging on a helium target.