Re: [Ifeffit] [Question about XANES] Hello I'm a graduate student in Korea

Doyoub's question is a common enough one that I added a section to the Athena user manual: http://bruceravel.github.io/demeter/documents/Athena/bkg/short.html My answer to Doyoub's question is much the same as Matt's. B On 03/17/2017 09:18 AM, Matt Newville wrote:

Dear Doyoub,

On Thu, Mar 16, 2017 at 10:59 PM, 김도엽(신소재공학과) mailto:mdyk100@postech.ac.kr> wrote:

Hello

I'm a graduate student at POSTECH in Korea.

Currently, I obtained XANES spectra over a narrow energy range and looked through the Athena manual

But, I'm kind of lost as to how exactly I'm supposed to normalize raw data

which only has XANES spectra.

It would be very generous of you if you help me figure this out

It's hard for us to answer questions that are so vague.

Generally, it is recommended to collect XANES spectra out to at least 100 eV (and better 300 eV) above the edge in order to get a decent normalization. Well, for "normal" hard X-ray spectra: for edges below about 3000 eV, you can often get by with less energy range.

If you don't have that, it is sometimes OK to pick an energy as far above the edge as possible and pick an edge step so that all the spectra is 1.0 at that energy. That is definitely prone to systematic biases in normalization. Furthermore, if your data is particularly noisy, it can add a lot of variation in the normalization to use just a single energy.

Which just brings me back to the original point: it's hard to say in general how to best handle XANES with a short energy range.

--Matt

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-- Bruce Ravel ------------------------------------ bravel@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/