Anomalous Dispersion in the Field of X-Rays


IN the course of an investigation with the purpose of getting more exact determinations of the wavelengths of the X-ray spectra, we have carried out a comparison of the lattice-constants of the two crystals, calcite and gypsum. In order to find the best possible value of this fundamental relation, we used a series of different spectral-lines with wave-lengths varying from 0.7 up to 5.2 Å.U. The measurements of the relation are given graphically in Fig. 1, where the values of are plotted against the wavelengths. As seen from the graph there are two marked discontinuities in the run of the curve. It is also seen that these two abrupt variations coincide with the wave-lengths of the absorption-edges of calcium and sulphur.

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HJALMAR, E., SIEGBAHN, M. Anomalous Dispersion in the Field of X-Rays. Nature 115, 85–86 (1925) doi:10.1038/115085c0

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