X-Ray Measurement of the Atomic Scattering Factor of Iron

Abstract

The x-ray integrated intensities of Bragg reflections of iron, copper, and NaCl powders were measured with monochromatic Fe $K_{\alpha }$ radiation. By investigating the effect of cold work on intensities of the metal powders and comparing the measured intensities of different orders with theoretical values, it was shown that extinction, surface roughness, and preferred orientation effects were negligible. The four measured iron reflections gave atomic scattering factors relative to either copper or NaCl which agreed, within experimental error, with values calculated from wave functions of the isolated iron atom. It is estimated that the experimental form factor for the lowest order reflection of copper and iron agrees with free-atom values to an error corresponding to the contribution of ± one free-atom-$3d$ electron. This is to be contrasted with results of Weiss and DeMarco, who concluded from single-crystal measurements that metallic iron has (2.3±0.3) $3d$ electrons, compared with 6 for the free atom.