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 f 440 (Ag K α) = 5.377 (15) and f 440 (Mo K α) = 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%.