Photoemission properties of metals

Photoemission has emerged over the last decade as a powerful method for studying electronic band structures. The applicabhty of the method to metals was established by Berglund and Spicer¹ in their landmark experiments on Cu and Ag. It had been believed, largely on the basis of optical absorption data, that the upper edge of the d bands in Cu and Ag lay at 2 and 4 eV below the Fermi level, respectively. Berglund and Spicer's measurements of the photoelectron energy spectra revealed these edges in a spectacular way and also uncovered some of the substructure of the d bands. Since then the technique has undergone some refinement and has been applied to a large number of materials. Photoemission measurements share the advantage of optical absorption measurements in that they are able to probe electronic states well removed from the Ferrni level. They have the added advantage that they give the initial and final energies as well as the frequencies of prominent optical transitions.