Thanks for the response Bruce
On Tue, May 16, 2017 at 2:43 PM, Bruce Ravel 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/
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