Elektronenstoßanregung und Polarisation der He II-Fowler-α-Linie

The hydrogen-like He II-Fowler-α-(λ=4686 Å)-line has been excited by single electron impact collisions with ground-state helium atoms. The excitation-ionization function was measured from the threshold (76 eV) to 300 eV in a pressure-independent range. A broad maximum of the excitation-ionization function was observed at 200 eV. The line excited by a parallel electron beam has been proved polarized in the energy range quoted above. The degree of polarization increased monotonously from 6% at 300 eV to 13% near the excitation threshold. Comparison was made with previous experimental work. No polarization of the Fowler-α-Line was reported in other investigations. The shape of the excitation-ionization function agrees with that ofJohn andLin. Comparison with theoretical calculations is not as yet possible because only results of Born approximations are available.