Photoemission spectra and band structures ofd-band metals. II. Experiments on Rh, Ir, Ni, Pd, and Pt

Abstract

Measurements of the photoelectron energy spectrum and its second derivative are reported for Rh, Ir, Ni, Pd, and Pt in the photon energy range $\hslash \omega =4\mathrm{} \mathrm{to} 11$ eV. Experiments were performed on clean samples, prepared by electron-bombardment evaporation, and on cesiated samples. The results on the different metals are compared with each other and with measurements on Cu, Ag, and Au. Relying primarily on the derivative spectra taken on cesiated samples, it is found that the variation of the profile of the spectrum with $\hslash \omega$ displays a consistent pattern from metal to metal. The pattern for one metal is obtained from that of the next by a uniform shifting and stretching of the electron energy scale, thus providing direct experimental support for the resonance picture of the $d$-band metals. The emergence at certain photon energies of some of the peaks in the $d$-band region of the spectra is attributed to the onset of transitions to the unoccupied seventh band. From this it is estimated that the plane-wave-like level $L_1$ is situated at 5.7, 4.3, 8.5, 8.0, 7.1, 6.1, and 3.6 eV above the Fermi level in Ni, Cu, Rh, Pd, Ir, Pt, and Au, respectively. An energy range in Ir and Rh where direct transitions are forbidden, but photoelectrons are observed, is discussed.