The Excitation of Polarization Waves in Bound Electronic States

The appearance of broad peaks in the electron energy loss spectra of elements in the first, second, and third long periods of the periodic table is discussed. It is shown that these peaks are similar to peaks which can be calculated by assuming absorption processes appropriate to ionization of bound states in these metals. By comparison with the calculated peaks and with the known optical constants of graphite a mode of excitation in the form of a collective polarization wave in these bound states is proposed. The possibility of deriving the optical constants of materials from their electron energy loss spectra is discussed.