The measurement of the X-ray scattering factors of silicon from the fine structure of Laue-case rocking curves

Laue-case rocking curves of a pair of crystals with nearly equal thickness display a detailed fine structure which is shown to be very suited to the determination of precise values of the atomic scattering factor f_g. Preliminary data thus obtained are f₄₄₀ (AgKα) = 5.377 (15) and f₄₄₀ (Mo Kα) = 5.402 (18) for silicon at 293 K. They agree well with the more precise data obtained in the past with the Pendellösung method using wedge-shaped crystals [Aldred & Hart (1973). Proc. R. Soc. London Ser. A, 332, 223–238]. The strength and the advantages of the new method are discussed. With proper optimization the rocking-curve method is assumed to measure f_g values with errors less than 0.1%.