Measurement of the Refraction of X-Rays in a Prism by Means of the Double X-Ray Spectrometer

Abstract

In the double spectrometer used, x-radiation was reflected from a crystal surface $A$ through a slit $S$ on to a second crystal surface $B$, and thence to the ionization chamber. Surfaces $A$ and $B$ were obtained by splitting a single crystal of calcite. The curve obtained for Mo $\mathrm{K}\alpha$ by rocking $B$ is a triangle with base about 8 seconds wide. The effect of interposing a prism of aluminum (angle 166°) between $S$ and $B$ was to shift the curve 5.62″ on the average, giving $1-\mu =1.68\mathrm{}\times {10}^{-6\mathrm{}}$. The value calculated from the Lorentz dispersion formula is 1.77×${10}^{-6\mathrm{}}$. For Cu $\mathrm{K}\alpha$ the shift was 5.53″ for a 116° prism, giving $1-\mu =8.4\mathrm{}\times {10}^{-6\mathrm{}}$ as compared with the calculated value 8.36×${10}^{-6\mathrm{}}$. The accuracy of this method is thus within 5 percent.