Interpretation of some features of the plasmon spectrum of simple metals

The influence of a periodic nonuniform background on the propagation of charge density waves in simple metals is studied. It is shown that the incorporation of spatial nonuniformity in the Vlasov-Poisson equations leads to a plasmon spectrum that is qualitatively consistent with experimental data. Namely, calculations show that charge density waves decay in a nonuniform medium even at a zero quasimomentum value; at some values of the inverse lattice vector, the dispersion curve has a negative slope.