Elastic energy losses due to scattering of fast electrons (20--40 keV) by crystals into large angles (_>_ 45 ~ are experimentally and theoretically investigated. Energy losses up to a few electron volts appear, which depend on the mass of the atoms composing the crystal, of the scattering angle, and of the primary energy of the electrons. These results agree with the assumption of elastic scattering by single atoms and not by the crystal as a whole. The width of the energy losses increases with the energy loss himself, and with the temperature of the crystal. In a first theoretical approximation this effect can be explained by the thermal motion of free atoms.
ProblemstellungElastisch gestreute Elektronen sind per definitionem solche, die keine Anderung des inneren Energiezustandes des Streuers verursachen. Trotzdem erleiden sie Energieverluste. Diese elastischen Energieverluste A E kommen im Laborsystem dutch die mit der Streuung verbundene Impuls/inderung zustande und ergeben sich aus den Erhaltungss/itzen von Energie und Impuls. F/it einen ruhenden Streuer der Masse M, an dem Elektronen der Masse mund der Prirn~irenergie E um den Winkel gestreut werden, wird dann f/Jr m ~ M der elastische Energieverlust: m 0
The electrostatic magnetic energy analyzer 1 consists of a Wien filter (crossed electric and magnetic fields) between two immersion lenses. The energetic resolution of the analyzer is calculated. The intensity problem in connection with the generation of a monoenergetic electron beam is discussed considering anomalous energy spread in high density beams. With an arrangement containing two analyzers of the same kind the resolving power is experimentally determined to 0.017 ev.
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