Abstract
The production of excited He+ ions by single-electron impact collisions with ground-state helium atoms has been observed by the optical method. The absolute value of the cross section for the collision process yielding the n=4→n=3 transitions (4686 Å) in He+ was determined for incident electron energies ranging from 60 to 470 eV. The excitation—ionization cross section exhibited a single broad maximum at 200 eV with an onset at 75 eV. The peak value of the cross section was 4.2×10—21 cm2. Stepwise ionization and excitation was nowhere in evidence. The excitation—ionization function obtained at a number of gas pressures was independent of pressure. Light yield was proportional to the electron beam currents. Comparison with previous experimental work and with theoretical calculations were made.
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