Hello all. I am getting confused with different comments how to determine the energy resolution of an XAS beamline. I think using peak fitting to determine the line width is a reasonable method. The basis of a XAS peak is the Voigt profile (a combination of a Lorenzian and Gaussian) The width of the Lorenzian equals the natural line width while the width of the Gaussian represents the experimental line width and some features Now here is question 1: What is the combination of the two profiles in the Athena peak fitting routine for the Pseudo-Voigt? Question 2: Is the sigma (Gaussian width) that delta E that represents the resolution - (E /delta E) ? Using a different program (Igor Pro) to determine the width gives different results because can only use a simple combination of Lorentz and Gauss (1:1). Thanks. Lisa