Resonance absorption at the L edges of tantalum: The white line

摘要: 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 LiF(200) crystal, (ii) synchrotron channel-cut Si(220) crystal. Our results similar to those reported by earlier workers except apparatus yields Ta highest resolution thus far. Of particular interest is sharp spike (white line) occurring ${L}_{\mathrm{III}}$ ${L}_{\mathrm{II}}$ but not ${L}_{\mathrm{I}}$ edge. We associated white line with an atomiclike allowed transition from $2{p}_{\frac{3}{2}}$ or $2{p}_{\frac{1}{2}}$ state vacant $5d$ states high density. However, quantitative comparison calculated band structure can be made because none existing calculations included effect core hole. In attempt understand lines, we present least-squares analyses edge in terms (a) Lorentzian profile (b) Breit-Wigner-Fano-type formula. latter, which was first suggested Cauchois Mott, appeared provide better fit asymmetric shape.