Absolute X-Ray Measurement of the Atomic Scattering Factor of Nickel

Joint measurements were made at Laboratorio F.N.A. Casaccia, Rome, Italy and at AMMRC, Watertown, Mass. to determine the atomic scattering factor of nickel. These studies were made using imperfect single crystals in transmission and applying a measured secondary extinction correction to the integrated intensities obtained with Mo $K\alpha$ and Ag $K\alpha$ radiation. A measurement of the incident beam power placed the measurements on an absolute scale. Three crystals were studied whose thicknesses $T$ were 31, 44, and 59 μ. Unlike similar measurements on aluminum by DeMarco, the apparent atomic scattering factors of nickel were found to depend on the reflection half-width $\Delta$, thus indicating the presence of primary extinction. By comparing the measured scattering factors as a function of $\frac{T^2}{{\Delta }^2}$, the dependence was found to be linear with a slope proportional to the square of the wavelength up to a difference of approximately 6% between extrapolated and observed scattering factors. The atomic scattering factors for the (111) and (200) reflections determined from an extrapolation to $\frac{T^2}{{\Delta }^2}=0\mathrm{}$ are found to be considerably lower than the theoretical value for the $3d^{8}4s^2$ configuration.