Hi Will, I worked with the Fe K-pre-edge, following the method of Wilke et al. (e.g. ref 20 in the Chaurand paper). Letting the peaks fit freely (but with shared FWHM and Gaussian/Lorentzian ratio) gave the best results. A few reasons to rely on the fitting program to give you the numbers: - The best number of peaks to fit can be affected by the resolution of your measurements. Crystal field theory might predict a specific number of transitions, but you might have non-local transitions, impurities, etc. that add extra peaks. Also, predicted transitions can be too close together to be fitted with individual peaks. - The Gaussian broadening and contribution (coming from the beamline resolution) is not always well-known. - The Lorentzian broadening and contribution (coming from core-hole lifetime-broadening, traditionally taken from theoretical values of Krause and Oliver in 1979) is also not easy to apply together with all unknowns mentioned above. As Chris mentioned, it is worth to find a good function to model the main edge. You can safely do that before fitting the pre-edge (ignoring the pre-edge peak). An arctangent + low-slope straight line + possibly a peak function should do the job. All the best. Alexey