L-edge x-ray-absorption systematics of the noble metals Rh, Pd, and Ag and the main-group metals In and Sn: A study of the unoccupied density of states in 4delements

X-ray-absorption L-edge spectra have been obtained for the noble metals Rh, Pd, and Ag and the main-group metals In and Sn. The systematics derived from these spectra reveal that (a) the x-ray-absorption near-edge structure (XANES) is primarily related to the density of states in these systems, (b) the energy distribution of the states above the Fermi level in noble metals is qualitatively consistent with the general band-theory description and semiquantitatively in agreement with the single-particle theory of Müller, Jensen, and Wilkins, and (c) the $L_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ ‘‘white-line’’ intensity ratio depends on the distribution of the $d_{5/2}$ and $d_{3/2}$ population above the Fermi level and this distribution deviates significantly from the statistical distribution when the d band of the metal is nearly full. The applicability of XANES in the investigation of the charge-distribution systematics in 4d elements is discussed.