Messung charakteristischer Energieverluste von Elektronen an leichtoxydierbaren Metallen im Ultrahochvakuum

Abstract

Energy losses of 34 keV electrons penetrating thin foils of Li, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, and Al are measured. The metals are evaporated and investigated in UHV (~10^-9 Lorr) with an apparatus constructed especially for this purpose. For all the alkali metals free electrons like behaviour is found with a surface and a volume plasma loss. Ca and Sr show more complicated structures. For most of the volume losses half width, dispersion and cut-off is measured. Surface losses are investigated for oxide-free surfaces with respect to angular distribution, dispersion and total excitation probability, and also the displacement due to oxidation is measured. A narrow loss line from the excitation of a surface wave at the Al/Mg interface is found at 12.8 eV in good agreement with the theoretically predicted value.