Rising Sun Envelope Method: An Automatic and Accurate Peak Location Technique for XANES Measurements

The lack of theoretical understanding of X-ray absorption near-edge structure (XANES) spectroscopy necessitates the development of analysis tools for its study. Here, an algorithm for judicious choice of local minima and maxima points of the XANES spectrum (experimental or simulated) is proposed, without any loss of information neither on the peak location nor on the peak strength. The method is named the Rising Sun Envelope Method and is based on successive regularizations of the spectral measurement that, according to parameter choices that are intrinsic to the measurements, keep the peak location and strength as invariants. This is the first method that finds peaks in XANES automatically, without depending on first derivative information. Nevertheless, a direct computation of the absorption edge is provided, overcoming the low quality and poor information given by inflection point computations based on the XANES second derivative: computations of inflection points from a higher quality cubic spline approximation are used instead. To illustrate its use, the algorithm is applied to XANES, electron energy-loss spectroscopy, and Raman spectra.