[Ifeffit] RE : problem with Athena's E0 !

[Arezki, Bahia]

Hi Bruce and Darek,


Bruce, thanks for the link, I am the only one here using xanes and athena ,  I learnt a lot from the Athena user's guide and the data I attached in my e-mail have been processed using the calibration and alignment dialogs and the procedure suggested.  So, I was sure that this was enough to set correctly E0.  

It seems that  ATHENA gives a  spurious value for  E0 (1728 eV for S36 xanes)   due to a shoulder in the rising part of the white line which is quite intense at  RT (s11) and decreases during the cooling of the sample. So, for s36 xanes at 10 K, ATHENA is simply taking the highest maximum in the 1st derivative which is this time higher in energy than the first one .

Darek, thanks a lot for looking in my data and for your comments. Yes,  the samples contain  Fe2+ ions. 

cheers,

Bahia



 -----------------------------------------------------------------
________________________________________
De : ifeffit-bounces at millenia.cars.aps.anl.gov [ifeffit-bounces at millenia.cars.aps.anl.gov] de la part de Zajac, Dariusz A. [dariusz.zajac at desy.de]
Date d'envoi : mercredi 1 juillet 2009 13:54
À : XAFS Analysis using Ifeffit
Objet : Re: [Ifeffit] problem with Athena's E0 !

Hi Bahia
I have opened your file and I see that everything is ok
Fe:K edge, reference at 7112 eV and your samples s11 at 7122.8 s32 at
7127 as a maxi of 1st derivative (for s32 is the highest maximum, but I
would take 7121.97 as E0)
it seams that Fe in your samples is not metallic one...
darek

>-----Original Message-----
>From: ifeffit-bounces at millenia.cars.aps.anl.gov
>[mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf
>Of Arezki, Bahia
>Sent: Wednesday, July 01, 2009 1:37 PM
>To: Bruce Ravel; XAFS Analysis using Ifeffit
>Subject: [Ifeffit] problem with Athena's E0 !
>Importance: High
>
>
>Hi all,
>
>I am using Athena (version: 08.058) to study the changes in
>the XANES profiles as a function of temperature of an
>organometallic compound containing Fe. I have a problem with
>the E0 value suggested by Athena : I noticed that it is not
>taking the same maximum in the first derivative.
>I am sending 2 examples of xanes taken at RT ( E0 guessed is
>1722.8 eV ) and 10 K  (1727.3 eV !), can any one help me
>please to solve this problem ? should I  force athena to take
>the first maximum at 1722 eV ?
>I  tough that  my spectra  have been properly calibrated:  I
>first calibrated the  iron foil -reference channel (E0=1712
>eV) of a sample xanes and then I aligned the rest of the
>reference channels to that one. I though this was enough to
>calibrate my data.  can you please tell me if my data
>processing is correct?
>
>I need to be sure about the E0 value in order to know the
>correct shift of the different xanes features as a function of
>temperature. Also, with a wrong E0 the normalization is not
>correct...did I miss an important step?
>
>I am having hard time with these basic questions...before
>using  linear combination analysis and peak fitting analysis.
>Of course I have already looked in the IFFEFIT archive, but I
>did not find such problem. I only found a question about a
>wrong E0 because taken before the edge which is not my case.
>
>Thanks so much for your time,
>
>
>
>Bahia
>

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