[Ifeffit] Peakfitting CeO2 data in Athena

[Stephanie Laga]

I had started with LSQ but switched to peak fitting because I was worried
about the Ce(IV) reference. I have data for bulk CeO2 and Ce(OH)4, but
doesn't this have some Ce(III) impurity in it? I'm not quite sure how to
account for this when I do LSQ.

Another challenge I've had is in using the Ce(IV) refs for our
nanoparticles, which are about 2-5 nm in diameter. Is there a good Ce(IV)
ref for nanos that are in this size range?

On Wed, Dec 7, 2016 at 2:37 PM, Matthew Marcus <mamarcus at lbl.gov> wrote:

> Instead of doing a bunch of peak fitting, try LSQ.  Use CeO2 (bulk or
> nanos) for one reference and some Ce(III) for the other.  Consistency
> check: see that the Ce(III) fraction is consistent over some set of Ce(III)
> references.
> Ce(III) has an assymetric white line, so it doesn't really fit a single
> gaussian.  CeO2, unlike other Ce(IV), has a shoulder on the first peak, and
> the first peak is shifted left a little with respect to other Ce(IV).
>         mam
>
>
> On 12/7/2016 10:33 AM, Stephanie Laga wrote:
>
>> Dear all,
>>
>> I am trying to extract the % Ce(III) from some CeO2 nanoparticle XAS
>> data. I have been using moved the peak fitting function in Athena to model
>> the XANES with an arctan background function and a series of gaussians.
>>
>> Looking through the literature I haven't seen too many specifics to using
>> this approach (rationale for choosing the widths of peaks or how to define
>> the background function). Similarly, doesn't seem to be much rationale for
>> choosing a 4 vs 5 peak fit for the XANES.
>>
>> My main question is then...1) Is there a rational for picking the
>> background function, specifically the height and width (can I let the
>> height vary or should I be keeping a constant arctan through all samples)?
>>
>> Any advice is greatly appreciated!
>>
>> Stephanie
>>
>>
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