Confirmation of standard error analysis techniques applied to EXAFS using simulations
Systematic uncertainties, such as those in calculated backscattering amplitudes, crystal glitches, etc., not only limit the ultimate accuracy of the EXAFS technique, but also affect the covariance matrix representation of real parameter errors in typical fitting routines. Despite major advances in EXAFS analysis and in understanding all potential uncertainties, these methods are not routinely applied by all EXAFS users. Consequently, reported parameter errors are not reliable in many EXAFS studies in the literature. This situation has made many EXAFS practitioners leery of conventional error analysis applied to EXAFS data. However, conventional error analysis, if properly applied, can teach us more about our data, and even about the power and limitations of the EXAFS technique. Here, we describe the proper application of conventional error analysis to r-space fitting to EXAFS data. Using simulations, we demonstrate the veracity of this analysis by, for instance, showing that the number of independent dat a points from Stern's rule is balanced by the degrees of freedom obtained from a 2 statistical analysis. By applying such analysis to real data, we determine the quantitative effect of systematic errors. In short, this study is intended to remind the EXAFS community about the role of fundamental noise distributions in interpreting our final results.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Chemical Sciences Division; Nuclear Science Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 980740
- Report Number(s):
- LBNL-2888E; TRN: US201015%%2113
- Resource Relation:
- Conference: 14TH INTERNATIONAL CONFERENCE ON X-RAY ABSORPTION FINE STRUCTURE (XAFS14), Camerino, Italy, 26-31 July 2009
- Country of Publication:
- United States
- Language:
- English
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