The relative photoemission intensity from the $\mathrm{Ag} 4d$ valence band (VB) was studied as a function of photon energy using 32-250 eV synchrotron radiation. A sharp decrease in intensity of more than an order of magnitude was observed in the range $100<\mathrm{}\hslash \omega <140\mathrm{}$ eV. At $\hslash \omega =140\mathrm{}$ eV the $4d$ cross section exhibits a minimum which is attributed to the radial node in the $4d$ wave function. High-resolution VB spectra were obtained in the energy range $60\le \hslash \omega \le 150$ eV. For $110\le \hslash \omega \le 130$ eV the relative heights of the two prominent valence-band peaks are inverted. This modulation is attributed to the strong variation of the atomic $\mathrm{Ag} 4d$ photoelectric cross section in this energy range. These results demonstrate the importance of carrying photoemission studies of $4d$-group metals to the $\hslash \omega \ge 150$ eV range in order to bridge the ultraviolet-photomission to x-ray-photoemission gap.

• Received 3 May 1976

DOI:https://doi.org/10.1103/PhysRevB.14.2411