X-Ray Plasmon Scattering of Lithium

Abstract

The plasmon dispersion relation for polycrystalline lithium has been obtained by investigating the plasma characteristic energy losses in the X-ray Compton-Raman spectra. The spectra of the X-ray scattered radiation have been analyzed using a double crystal spectrometer with two calcite crystals. The plasmon energy has been recorded for the following wave vectors: k =1.1, 1.0, .95, .895, .80, .70, .60 and .40Å -1 . Each value of k has been obtained using six different incident wave lengths and the appropriate scattering angle. The wave lengths are: CuK α1 , K α2 , K β ,CrK α1 , K α2 , K β . The results show that the dispersion relation: \(\omega_{k}{=}\omega_{0}\left(1+3\cdot\frac{k^{2}{V_{F}}^{2}}{10{\omega_{0}}^{2}}+\cdots\right)\), is a good approximation. Also, it is clear that the density fluctuation excitation spectrum consists of a very narrow line. Plasmons with k > k c have been observed. No conclusion can be reached about plasma lines for the scattering angle φ=0°.