THEORY FOR THE COMPLEX DYNAMIC STRUCTURE FACTOR OF AN ELECTRON-GAS

The anomaly observed in the dynamical structure factor S(k, omega ), of various metallic systems is explained by considering processes in which a plasmon decays into an electron-hole pair plus a plasmon in addition to the usual RPA single-pair final state. The splitting in the spectrum is shown to result from the existence of two poles in S(kz) for Imz<0 and k<2k F. The observed structure in S(k, omega ) is reproduced almost exactly.