The calculation of p-wave phaseshifts for positron-helium scattering

The Kohn variational method is used to calculate low-energy p-wave phaseshifts for positron-helium scattering with trial functions which are more flexible than those used previously by the present authors. Detailed investigations are made into the convergence of the results with respect to systematic improvements in the trial functions and close similarities are found with the convergence pattern of the corresponding results for positron-hydrogen scattering. These similarities are exploited to obtain more accurate positron-helium phaseshifts with a relatively modest amount of computational effort. Improved values of the annihilation rate parameter Zsub(eff) are also given. (author)