Electron excitation from the ground state of helium to the 31D state

The sensitivity of the cross section to the ground-state wave function is investigated by considering the Born approximation to the scattering amplitude in the limit of zero momentum change. The total Born cross section is calculated using two alternative formulations and at an energy of 108 ev the results obtained are smaller than the value measured by Heddle and Gabriel in 1960 by a factor of at least 2. Further Born calculations indicate that coupling with 3 1 P as an intermediate state is not important but calculations made by Somerville in 1963 suggest that coupling to 2 1 P may be important.