Characteristic Energy Losses of 8-keV Electrons in Liquid Al, Bi, In, Ga, Hg, and Au

Characteristic loss spectra have been obtained in a reflection scattering geometry for liquid Al, Bi, In, Ga, Hg, and Au and, in the case of Al, Bi, and Au, for the same specimens in the solid phase. Peaks due to surface and volume plasmon excitation dominated the loss spectra for all elements except Au. The relative intensity of these peaks varied rapidly with scattering angle for the Al, Bi, In, and Ga specimens, but there was little angular variation when Al, Bi, or Au was evaporated onto a frozen substrate of the same element. The Al plasmon losses varied with temperature and changed at the melting point as would be expected from the known density variation. Changes in the Bi plasmon energy losses on melting and changes in other structure on melting have been interpreted in terms of band-structure changes. The peaks in the gold loss spectra appeared to become broader and less distinct on melting, from which it was concluded that the Au excited states had shorter lifetimes with increased disorder. In general, however, the liquid- and solid-state spectra of the same element were similar, thereby showing that for these materials there was not a large change in the electronic structure on melting.