RELATIVE DIFFERENTIAL CROSS-SECTIONS FOR THE ELECTRON-IMPACT EXCITATION OF THE 3(3)P, 3(1)D AND 3(3)D STATES OF HELIUM

We present measurements of relative differential cross sections for the electron impact excitation of the 3(1)D, 3(3)D and 3(3)P states of helium at energies of 40, 45, 60 and 80 eV and for scattering angles ranging from 30-degrees to 120-degrees. The results are extracted from existing data of electron-photon coincidence experiments. Our results are in agreement with distorted wave calculations. We point out the consistency of our results with the angular behaviour of the coherence parameter rho00 also obtained from these coincidence experiments.