Abstract
The theoretical differential cross section for the elastic scattering and for the excitation of optical transitions in helium by electron impact has been refined in Born approximation by use of the two parameter Eckart eigenfunction for the ground state and for the excited states.
The angular distributions of 25 kev electrons scattered elastically and inelastically by helium were measured in the angular range 2·3·10−4≦ϑ≦4·10−2. The intensity distribution of the elastically scattered electrons is in accordance with the theoretical curve forϑ>7·10−3 and is disturbed at smaller angles by the primary beam.
Normalization of the experimental values to the theoretical elastic differential cross section leads to agreement between the experimental differential cross section for the excitation of the 21 P and 31 P state and the scattering formulae given in this paper. There are small systematic deviations (<20%) for the 21 P differential cross section in the angular range 3·10−3<ϑ<1·10−2 only. The oscillator strength of these two transitions has been determined from the scattering measurements:f 21=0·312±0·04 andf 31=0·0898±0·006.
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Für das Interesse, das Herr Professor Dr.Boersch der Durchführung dieser Arbeit entgegenbrachte, und seine wertvollen Hinweise, bin ich ihm sehr zu Dank verpflichtet. Herrn Dr.Schoenebeck danke ich für anregende theoretische Diskussionen.
Die Untersuchungen wurden durch Bereitstellung von ERP-Forschungsmitteln in dankenswerter Weise gefördert.
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Geiger, J. Elastische und unelastische Streuung von Elektronen an Gasen. Z. Physik 175, 530–542 (1963). https://doi.org/10.1007/BF01375345
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DOI: https://doi.org/10.1007/BF01375345