 | Acta Crystallographica Section D Acta Crystallographica Section D BIOLOGICAL CRYSTALLOGRAPHY |
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![[Figure 1]](ea5041fig1mag.jpg)
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Figure 1
Graphical representation of a three-beam case. The lattice planes of g, of h and of h − g are shown as bold lines and the incident beam is shown as double lines. The primary wave h is shown as a dotted line, as is the weaker umweg wave, which is the second reflection of the h wave from the (h − g) planes in the g diffracted-beam direction. The secondary wave g is shown as a dashed line, as is the weaker umweg wave in the h direction. Strong waves are shown in bold. The experimentally measured quantity is the intensity in the direction of h as g is brought in and out of reflecting condition by a sample rotation called a Ψ scan. The rotation axis of the Ψ scan is illustrated with a dot–dashed line. The umweg wave in the direction of the h diffracted beam will interfere with the primary wave h (the fine dashed line interferes with the bold dotted line). The observed intensity change will depend on the relative amplitudes and the difference between the phase of the umweg wave and the phase of h: φ(g) + φ(h − g) − φ(h). |
![[Figure 1]](ea5041fig1.jpg)
| BIOLOGICAL CRYSTALLOGRAPHY |
ISSN: 1399-0047
