International
Tables for
Crystallography
Volume B
Reciprocal space
Edited by U. Shmueli

International Tables for Crystallography (2006). Vol. B, ch. 4.4, p. 457   | 1 | 2 |

Figure 4.4.4.1 

P. S. Pershana*

aDivision of Engineering and Applied Science and The Physics Department, Harvard University, Cambridge, MA 02138, USA
Correspondence e-mail: pershan@deas.harvard.edu

[Figure 4.4.4.1]
Figure 4.4.4.1

(a) Schematic illustration of the geometry and (b) kinematics of X-ray scattering from a freely suspended smectic film. The insert (c) illustrates the orientation of the film in real space corresponding to the reciprocal-space kinematics in (b). If the angle [\varphi = \theta], the film is oriented such that the scattering vector is parallel to the surface of the film, i.e. parallel to the smectic layers. A `[Q_{L}] scan' is taken by simultaneous adjustment of [\varphi] and [2\theta] to keep [(4\pi / \lambda) \sin (\theta) \cos (\theta - \varphi) = (4\pi / \lambda) \sin (\theta_{100})], where [\theta_{100}] is the Bragg angle for the 100 reflection. The different in-plane Bragg reflections can be brought into the scattering plane by rotation of the film by the angle [\chi] around the film normal.