Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2022 / Paper 4 / 57 / d / Solution

Write the ordinary structure factor as $F_0=|F_0|e^{i\varphi }$ and use $F=F_0+19.2i$. The intensities implyConsequently $\sin \varphi =0.43893$, and the two possible ordinary phases areThe twofold ambiguity is expected from a single anomalous-intensity constraint. The calculation assumes that the specified imaginary increment is the only change requiring inclusion; an additional unspecified real dispersive change could not be reconstructed from these data alone.