Determination of the absolute structure factor for the forbidden (222) reflection in silicon using 0.12-Åγrays

A room-temperature determination of the absolute structure factor for the forbidden (222) reflection in silicon has been conducted at the University of Missouri Research Reactor with 103-keV gamma rays. The measured structure factor of $F(222)=1.456$ is in excellent agreement with five of the earlier intensity measurements, and is significantly different from any value determined using Pendell\"osung techniques. An increase in accuracy over previous intensity measurements by a factor of between 2 and 10 has been achieved and is made possible through the use of monoenergetic, short-wavelength gamma rays, which allow absolute measurements to be made in Laue geometry on relatively thick crystals ({~}1 mm) without encountering extinction problems.