Thanks for the response Bruce On Tue, May 16, 2017 at 2:43 PM, Bruce Ravel <bra...@bnl.gov> wrote:
> On 05/16/2017 01:31 PM, Stephanie Laga wrote: > >> >> I have a (hopefully) quick question about calculating oxidation state of >> CeO2 at the L3 edge. >> >> When calculating ox state by taking the ratio of peak areas, is the >> pre-edge feature for Ce included in this calculation? This point isn't >> clear to me from looking at various papers. >> >> I've attached an image from Bernardi 2015, which shows that the %Ce III >> calculation doesn't include the fitted pre-edge feature A. I'm not sure >> why this would not be included? Is this because we only consider 2p > 5d >> transitions and the pre-edge is 2p > 4f (forbidden) transition? >> >> > > I am not sufficiently knowledgeable about CeO2 specifically to answer your > question specifically. However, there are some general principles that > apply. > > The concept here is to come up with a set of peak shapes that describe the > shapes of the end member spectra. Those two sets of peaks, taken together, > represent the contribution to the spectra from each end member. Sum the > areas of each set of peaks, that represents the contribution. > > You then fit all of both sets of peaks to an unknown spectrum and sum up > each set. You now have enough information to quantify the amount of each > end member. > > So, in general, yes, you would include the fitted peak A because that is > part of your quantification metric. So, I disagree with the formula in the > figure you attached. But peak A is small, so neglecting it has scant > impact on the result. > > Some caveats: > > 1. You must be very careful about normalization. If you do not normalize > consistently, then you will introduce systematic error in the phase > quantification. > > 2. You must use the same step-like function for both end members and for > the unknowns. If the step function changes, then the areas under the peaks > will change, introducing systematic error. > > It would be interesting to compare this to linear combination analysis to > see if you get the same answers.... > > HTH, > B > > -- > Bruce Ravel ------------------------------------ bra...@bnl.gov > > National Institute of Standards and Technology > Synchrotron Science Group at NSLS-II > Building 743, Room 114 > Upton NY, 11973 > > Homepage: http://bruceravel.github.io/home/ > Software: https://github.com/bruceravel > Demeter: http://bruceravel.github.io/demeter/ > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit >
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
