Optical absorption in the4dtransition metals from 20 to 250 eV

Abstract

The optical absorption of Y, Zr, Nb, Mo, Rh, Pd, Hf, and W has been measured between 20 and 250 eV using synchrotron radiation from the Tantalus I electron storage ring. The samples were thin, self-supporting films, and transmission measurements were performed at normal incidence. The results were compared with our results from previous reflectivity measurements in the range of overlap (20-40 eV), as well as with electron-energy-loss measurements where available. The data were interpreted in terms of largely atomiclike transitions of the $4p$-to-$4d$ type. Arguments were presented to support this interpretation, and analogies were drawn to the higher-energy $4d$-$4f$ transitions in the rare earths. Structures were observed on the low-energy side of the onset which were interpreted in terms of the spin-orbit splitting of the initial $4p_{\frac{1}{2}}$ and $4p_{\frac{3}{2}}$ states. The broadening of the $p$-$d$ structure was interpreted qualitatively in terms of multiplet splitting and autoionization processes. At higher energy, structures related to $3d$ transitions were observed.