Glauber Cross Sections for Excitation of the2S1State of Helium by Electron Impact

The Glauber amplitude for describing collisions of charged particles with two-electron atoms, resulting in transitions between spherically symmetrical states, is reduced to a readily computable form. Application is then made to the $2{}_{}{}^1{}_{}{}^{}S\leftarrow 1{}_{}{}^1{}_{}{}^{}S$ transition in helium, for which angular distributions are determined for 26.5-, 34-, 50-, and 83-eV incident electrons. Comparison with experiment shows that the Glauber theory is capable of accurately predicting the angular distributions for even our lowest-energy calculation. In particular the theory predicts the recently observed structure in the differential cross section. The energy dependence of the "apparent" generalized oscillator strength is also demonstrated for incident energies in the range 300-1100 eV.