Higher-Derivative Photoemission Spectra and the Relativistic Band Structure of Gold

Following a prescription by Ehrenreich and Hodges, a relativistic band structure for Au has been constructed by the insertion of spin-orbit coupling into an originally nonrelativistic interpolation scheme. The bands are used to compute the energy distribution of the joint density of states D(E, ω) and its second derivative with respect to energy D^''(E, ω). Peaks in -D^''(E, ω) are found to correlate quite well in energy location with structure in experimental higher-derivative photoelectron-energy spectra measured on cesiated Au. The comparison is made with previous data and with supplementary spectra presented here. Profile changes in the experimental spectra on varying the photon energy ω are also reasonably well accounted for. The density of states computed from the same band structure shows d-band peaks at 2.65, 4.00, 4.50, 5.05, 6.35, 6.85, and 7.60 eV below the Fermi level. From the derivative spectra at the lower photon energies, the L₆^-(L_2^')→L₆⁺(L₁) band gap in Au is estimated to be 4.0 eV.