Plasmaschwingungen in Al,Mg, Li,Na und K angeregt durch schnelle Elektronen

We report on energy loss experiments with 50 keV electrons transmitted through thin films of the metals Al, Mg, Li, Na, and K. The valence electrons of these materials behave like a gas of free electrons to a good approximation and, in particular, give rise to significant collective effects. Since these substances oxidize rapidly they were evaporated and studied in ultra high vacuum. The apparatus and the measurement technique are described. Measurements of loss spectra for different electron scattering angles yield the volume plasmon dispersion curve and the dependence of the damping of the volume plasmon on the wave vector. New experimental values of the energy and the half width of the plasma oscillations and the coefficients of dispersion and damping are given. In addition, the results of some measurements on surface plasmons are presented. There are significant deviations from the predictions of the simple electron gas model.