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Anomalous signal (see here)

Set the ANOMALOUS flag when scaling and scale and postrefine; the output .sca file will have separate I+ and I- and scalepack treat these as two separate measurements.

To detect the presence of anomalous signal examine the Chi^2 values in the Table "Chi^2 and R-Factor vs. Resolution"; if errors scale factors are reasonable, and there is no anomalous signal, the curves of Chi^2 resolution dependence should be flat and ~1 for scaling with merged and un-merged Friedel pairs. If Chi^2>1 and there is clear resolution dependece of the Chi^2 for scaling with merged Friedel pairs, this is a strong indication of the presence of anomalous signal.


If fewer than 0.5% of the reflections are rejected this is acceptable (considered normal). Greater than 1% means possible problems with indexing, integration, space group assignment, or data itself.