RESONANCE-ABSORPTION AT THE L-EDGES OF TANTALUM - WHITE LINE

The x-ray absorption spectrum at the L edges of tantalum has been measured on two spectrometers that are equipped with: (i) a conventional bremsstrahlung source and a LiF(200) crystal, and (ii) a synchrotron source and a channel-cut Si(220) crystal. Our results are similar to those reported by earlier workers except that the apparatus (ii) yields a Ta L spectrum of the highest resolution reported thus far. Of particular interest is the sharp spike (white line) occurring at the LIII and LII but not at the LI edge. We associated the white line with an atomiclike allowed transition from the 2p32 or 2p12 state to the vacant 5d states of a high density. However, a quantitative comparison with the calculated band structure can not be made because none of the existing calculations has included the effect of a core hole. In an attempt to understand the white lines, we present two least-squares analyses of the Ta LIII edge in terms of (a) a Lorentzian profile and (b) a Breit-Wigner-Fano-type formula. The latter, which was first suggested by Cauchois and Mott, appeared to provide a better fit to the asymmetric line shape. © 1979 The American Physical Society.