Experiments on the Variation of the Atomic Structure Factor of Nickel with X-Ray Wave-Length

Abstract

X-ray measurements have been made with a vacuum ionization spectrometer on powdered nickel to determine the variation of the atomic structure factor in the region of the $K$ absorption edge, $\lambda =1.4839\mathrm{}\mathrm{A}$, and as far out as possible on the long wave-length side. Powdered NaCl and LiF have been used as comparison substances. Extensive measurements over a range of wavelengths from 0.560 to 2.74A have been made. Conclusions: The experimentally determined dispersion curve for the atomic structure factor of nickel, based upon the difference between measured structure factor values on the long and short wave-length side of the $K$ absorption edge, does not agree in shape with the theoretical curve of Hönl. The experimental curve rises more rapidly from the absorption edge and is then flatter than the theoretical curve. The two curves come into closer agreement at longer wave-lengths. The maximum discrepancy between theory and experiment is about 0.9 electron at $\frac{\lambda }{{\lambda }_K}=1.11\mathrm{}$. The predicted invariance of the structure factor decrement due to $K$ electrons with $\frac{\left(sin\theta \right)}{\lambda }$ is again confirmed.