[Ifeffit] Ke

[Sin Yuen Chang]

Dear Pushkar/Ke, 

I normally use different e0 values in Athena based on what I want to do:

1. e0 for energy scale calibration  
A generally accepted method is to use derivatives to match the energy scales, as described in the previous threads. I apply this to a known standard and shift the energy scale of the other spectrum that I want to calibrate by the same extent.    

2. e0 in EXAFS modelling 
After I know that the energy scale I have is correct, then in EXAFS modelling, e0 is now the point where your EXAFS backscattering starts. That's why we are trying to avoid white lines here. 

It took me some time to figure out that e0 could mean several different things.

There is a rich history in IFEFFIT discussion on e0, examples: 
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2014-June/011841.html
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2014-June/011836.html
http://cars9.uchicago.edu/pipermail/ifeffit/2004-June/005614.html

Best wishes,
Sin Yuen

-----Original Message-----
From: ifeffit-bounces at millenia.cars.aps.anl.gov [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf Of Carlo Segre
Sent: 15 October 2014 22:56
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Ke


Either way is fine but I would suggest taht you not use the calibrate function, just read off the zero crossing and put it into the E0 location. 
Calibrate actually shifts the data and that is not necessarily what you want to do, particularly if you are comparing spectra..

Carlo

On Thu, 16 Oct 2014, Pushkar wrote:

> Dear Ke
> Is there a reason you use first derivative?? I thought if you take second derivative on Athena and then click find zero and then calibrate that value is the correct way. I am learning XAFS myself for the first time and I am novice too. So may be I make no sense but just want to confirm if I am not doing anything wrong. What's your stake in this??
> Pushkar
>
> Pushkar Shejwalkar
> Post-doctoral researcher, JSPS fellow, Catalysis Research Center 
> Hokkaido University, Sapporo
> Japan-0010020
>
>
>> On १६ ऑक्टो, २०१४, at १२:२७ म.पू., Ke Yuan <keyuan at umich.edu> wrote:
>>
>> Hello Sin Yuen,
>>
>> Thanks for forwarding me that study materials on E0.
>>
>> I use Athena to find the highest peak on the fist derivative of the spectra and pick that value as E0. I think I did not put E0 above this value. I will try to put it on the high energy side to see what will happen.
>>
>> Tks!
>> Ke
>>
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--
Carlo U. Segre -- Duchossois Leadership Professor of Physics Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://phys.iit.edu/~segre   segre at debian.org