Cross Sections for the Formation of Excited States in a Helium Target by the Impact of 0.15- to 1.0-MeV Protons and Deuterons. II. Comparison with Theory

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Abstract
Experimental data on the excitation of helium by the impact of protons in the energy range 0.15-1.0 MeV, published in the preceding paper, are compared with available theoretical predictions. The general predictions of the Bethe-Born approximation are examined, and empirical values are determined for the constants in the equations which will allow the prediction of the behavior to be expected at higher energies and for different projectiles. In the case of quadrupole transitions, the accuracy of available Born-approximation predictions is poor, but reasonable agreement is found with the experimental data. Accurate calculations in the distortion approximation are available for the excitation of dipole transitions, and these are found to agree very well with experiment down to 75-keV impact energy. The data for the simultaneous removal of one electron and the excitation of the remaining electron are examined qualitatively in the light of theoretical predictions and compared with other two-electron excitation processes.