Analysis of low-energy scattering cross sections

The e--He differential scattering cross section measurements for selected energies between 2 and 19 eV have been re-analysed to obtain phaseshifts and associated errors which are consistent with the measurements. The phaseshifts obtained from different angular distribution measurements are shown to be consistent with each other within their associated errors and are also consistent with the best available phaseshifts determined by theory. These phaseshifts have also been used to determine total and momentum transfer cross sections which are compared with direct determinations of these quantities. The re-analysis of the differential cross section measurements does not reduce the uncertainty which presently exists in the total cross section at lower energies. It is suggested that the uncertainty, which is as large as 20% at the lower energies, can be reduced by more precise measurements and analysis of the 2S resonance profile at 19.35 eV coupled with precise relative measurements and analysis at other energies and/or accurate cross section calculations which include an ab initio error determination. (author)