Photoelectron Energy Spectra and the Band Structures of the Noble Metals

Photoelectron energy distributions and their second derivatives have been measured on Cu, Ag, and Au in the photon energy range 4.0-11.4 eV. Samples were prepared by evaporation in ultrahigh vacuum and were coated with an approximate monolayer of Cs or Na in order to lower the work function. The experimental energy spectra show much new structure, and in each metal there are instances of behavior indicative of direct transitions from the $d$ bands. The predictions of the direct-transition model have been calculated by performing numerical evaluations of the energy distribution of the joint density of states (EDJDOS) using interpolated band structures. Energy locations of structure in the experimental spectra are compared with peak loci in the theoretical EDJDOS. The agreement is found to be good for Cu and Ag, and reasonable (in view of the nonrelativistic nature of the calculations) for Au. Calculations of the density of states and the interband joint density of states are also presented, and the latter are compared with experimental values for ${\epsilon }_2$.