Benchmark Integral Cross Sections for Electron Impact Excitation of the n=2 States in Helium

Abstract

In this paper, we present integral cross sections (ICS) for electron impact excitation of the n=2 levels in helium in the impact energy range of 23.5 eV to 35 eV. The ICS of each final state, 23S, 21S, 23P and 21P, has been determined by integration of the angular differential cross sections (DCS) over all of 0° to 180°, where those DCS were obtained from both our previous experiments and the extrapolation using the convergent close coupling calculation. The present experimental ICS for the optically allowed 21P transition state are also compared with those obtained from the BEf-scaling method. Very good agreement between the experimental and BEf-scaled 21P ICSs is generally found in the measured impact energy region.