Diffuse Scattering of X-Rays from Sodium Fluoride. III. Using Sensibly Monochromatic Radiation

The Mo $K\alpha$ lines, together with a small amount of the continuous spectrum of half the wave-length, were isolated by crystal reflection and scattered from a crystal of NaF at room temperature. Ionization currents were measured by using an FP-54 pliotron and d.c. amplifier. Comparison was made with the scattering at 90° from paraffin, and $S_{\mathrm{class}}$ was determined between $x=0.1\mathrm{}$ and $x=1.0\mathrm{}$. It agrees fairly well with the $S_{\mathrm{class}}$ obtained by the author in a previous research using a band of wave-lengths. Comparison is made between the observed $S_{\mathrm{class}}$ and these computed by theory from wave-mechanics atomic structure factors, using the assumptions of zero-point-energy or no zero-point-energy. The discrepancy between experiment and theory, especially if the former assumption is correct, seems considerable enough to imply the need for some modification in the theory, probably in the incoherent scattering term.