Plasma Oscillation of Electrons in Be, Mg, Al, Si, Ge, Sn, Sb and Bi

The plasma oscillation of electrons in Be, Mg, Al, Si, Ge, Sn, Sb and Bi has been studied using the method of energy analysis of electrons passed through thin foil of those solids. The energy loss value Δ E , the dispersion relation, i. e. the dependence of Δ E on the scattering angle θ, the angular dependence of the intensity, the half breadth of Δ E , and the cutoff scattering angle θ c (corresponding to the cutoff wave number k c ) were measured by the photometric method. The angular distribution of the intensity does not agree with θ -2 law given by Ferrell, but shows θ 1.6∼-1.7 dependence. The curvature of Δ E vs. θ curve for Be, Mg, Al and Si agree well with the theoretical values calculated by the free electron theory, but those for Ge, Sn and Sb are 20∼30% larger than the corresponding theoretical values, and that for Bi is twice as large as the latter. The half breadths of energy loss peak due to the plasma oscillation increase with increase in the scattering angle. Specimens of Ge were studied in the crystalline and in the amorphous states. The half breadth of energy loss peak of crystalline Ge is narrower than that of amorphous Ge, and the total cross section of the excitation of plasmon in both specimens are almost the same. The ratios of the total cross sections of the excitation of the plasmon in Al and in Be, and of that in Al and in Mg were measured.