Geiger-Müller Counter Measurements of Reflected MoKαX-Rays from Powdered Zinc

Volz has used the formula $n=n_0\exp (-\frac{n_0}{2.78n_m})$ where $n$ is the observed counting rate of the system, $n_0$ is the rate of production of pulses in the counter and $n_m$ is the maximum possible random counting rate. It was found that $n_0$, calculated from $n$ and corrected for background count, varied as the inverse square of the distance from a gamma-ray source. Further, the absorption coefficient of Mo $K\alpha$ rays in aluminum was found to have the correct value when measured by means of this formula. Thus the formula was satisfactory. The absolute $F$ values were obtained by comparison of the ($11\overline{2}2$) reflection from zinc with the (420) reflection from KCl. This gives $F\left(11\mathrm{}\overline{2}2\right)=13.9$. Brindley, using Cu $K\alpha$ rays, obtains $F\left(11\mathrm{}\overline{2}2\right)=12.0$. The difference is caused by dispersion. The $F$ values for other reflections very closely agree with those found by Brindley for Cu $K\alpha$ rays, when his values are corrected for dispersion. The very weak (0004) reflection, which was not obtained by Brindley, was found to have an $F$ value of about 10.6. Jauncey and Bruce's values of the amplitudes of the thermal vibrations parallel and perpendicular to the $c$ axis fit these results better than do Brindley's.