Photoemission from Cu, Ag, and Au in the 10- to 27-eV Energy Range

Measurements of high-resolution photoemission-energy distributions have been extended beyond 11.6 eV (LiF-window cutoff) for Cu, Ag, and Au. Surprisingly sharp structure ($\Delta E\sim 0.3$ eV, i.e., resonance $\Delta \equiv \frac{E}{\Delta E}\simeq 50$) is resolved at these high energies. These new results show $d$-band widths of 3.0, 3.5, and 5.7 eV for Cu, Ag, and Au, respectively, and show dramatic evidence (nonstationary structure and amplitude effects) for direct transitions.