Abstract
The effect of distortions on the (e,2e) spectroscopy of helium is examined. In particular, it is found that distortions contribute significantly to the (e,2e) cross section for transitions to both the n=1 ground state and n=2 first excited states of He+ at incident energies as high as 1200 eV. This raises questions about the use of uncorrected (e,2e) cross sections at high momenta to test the accuracy of correlated wavefunctions for the ground state of helium. By numerically correcting new experimental data for distortions, it is possible to obtain improved agreement between experiment and calculated values of the momentum space overlap integral (f mod exp(iq.r)g). The helium wavefunction used in the calculations is a recent state-of-the-art CI wavefunction which gives better than 98% of the correlation energy.