High-Resolution X-Ray Photoemission Spectrum of the Valence Bands of Gold

TLDR

High‑resolution gold‑valence‑band photoemission spectra were measured on a single‑crystal gold sample using monochromatized Al Kα radiation, then corrected for background and scattering and compared with broadened theoretical density‑of‑states functions. Relativistic band‑structure calculations with full Slater exchange best reproduce the spectrum, while fractional exchange over‑widens the d bands; the X‑ray and UV spectra agree, indicating little photon‑energy dependence and no strong matrix‑element modulation.

Abstract

High-resolution gold-valence-band photoemission spectra were obtained by the use of monochromatized $\mathrm{Al} K\ensuremath{\alpha}$ radiation and a single-crystal specimen. After background and scattering corrections were made, the results were compared directly with broadened theoretical density-of-states functions. The following conclusions were drawn: (i) Relativistic band-structure calculations are required to fit the spectrum. (ii) Both the Korringa-Kohn-Rostoker calculation of Connolly and Johnson and the relativistic-augmented-plane-wave calculation by Christensen and Seraphin give density-of-states results that (after broadening) follow the experimental curve closely. (iii) Of the theoretical functions available to date, those with full Slater exchange agree best with experiment (perhaps because of a cancellation of errors). Fractional ($\frac{2}{3} or \frac{5}{6}$) exchange gives $d$ bands that are too wide. (iv) Eastman's 40.8-eV ultraviolet photoemission spectrum is similar to the x-ray spectrum, suggesting little dependence on photon energy above 40 eV. (v) Both (ii) and (iv) imply an absence of strong matrix-element modulation in the photoemission spectrum of gold.