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Updated: May 24, 2026
15:04
Rejection of Fluorescence Background in Resonance and Spontaneous Raman Microspectroscopy
Published on: May 18, 2011
On the significance of Bragg reflections
Mads Ry Vogel Jørgensen1, Helle Svendsen, Mette Stokkebro Schmøkel
1Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Aarhus C, Denmark.
Acta Crystallographica. Section A, Foundations of Crystallography
|February 18, 2012
Summary
Bragg diffraction data significance was re-evaluated. Processing errors, not inherent data quality, caused previously observed W(Bragg) values > 1. The SORTAV program
Area of Science:
- Crystallography
- Materials Science
- Data Analysis
Background:
- The significance of Bragg diffraction data is typically assessed using the W = (I(1/2))/(σ(I)) descriptor.
- Data processing steps like background subtraction and absorption correction can introduce errors, theoretically leading to W(Bragg) < 1.
Discussion:
- Previous studies reported W(Bragg) > 1, which is now shown to be an artifact of neglecting a data scale factor in uncertainty calculations.
- The empirical error model in SADABS significantly underestimates data significance and produces unusual error distributions.
- Error estimation using the variance of abundant intensity data, as in SORTAV, provides more reliable significance values.
Key Insights:
- Corrected W(Bragg) values for data on an absolute scale are consistently below unity.
- The SADABS program's error estimation model is shown to be problematic.
- The SORTAV program's error estimation approach is recommended for processing Bragg diffraction data.
Outlook:
- Modern area detectors facilitate the collection of highly redundant data, supporting robust error estimation.
- Further investigation into data processing and error estimation models is crucial for accurate crystallographic analysis.
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