[Ifeffit] Projekt with the "flatten-problem"

[Barton, David (DG)]

Jens,

It appears to me that the E-shift is causing the problems with the step in the pre-edge data. Shelly's data only appears to remove the step because the pre-edge and the extrapolated post-edge plots are nearly parallel. If you adjust the Normalization range in Shelly's data you will see the step appear again.

However, if you set the E-shift to zero and reset Eo, pre-edge range, and normalization range (to your liking) you will see that the step is goes away.  So the work around would be to subtract the E-shift from your Raw data, then import into Athena and do not use any E-shift.

Bruce or Matt may have to comment, but it appears to me that the normalization/flatten routine may not be dealing with the E-shift appropriately.

Dave

>-----Original Message-----
>From: ifeffit-bounces at millenia.cars.aps.anl.gov 
>[mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf 
>Of Kelly, Shelly D.
>Sent: Thursday, January 11, 2007 11:11 AM
>To: XAFS Analysis using Ifeffit
>Subject: RE: [Ifeffit] Projekt with the "flatten-problem"
>
>Hi Jens,
>
>I believe the problem is related to the structure in the data 
>before E0.
>If you choose e0 to be at the beginning of the structure then 
>the normalization is handled better by Athena.  Take a look at 
>the attached project file.  The first data set with e0 on the 
>edge as you would choose for EXAFS analysis (e1) shows the 
>error that Jens reported.  The second data set with a lower 
>value for e0 at the beginning of the structure (e2) gets the job done.
>
>Cheers,
>Shelly
>
>---------------------------
>Shelly Kelly
>Argonne National Laboratory
>Bldg 203, RM E113
>9700 S. Cass Ave
>Argonne, IL 60439
>
>Molecular Environmental Science Group
>www.mesg.anl.gov
>skelly at anl.gov
>phone: 630-252-7376
>
>
>> -----Original Message-----
>> From: ifeffit-bounces at millenia.cars.aps.anl.gov [mailto:ifeffit- 
>> bounces at millenia.cars.aps.anl.gov] On Behalf Of Jens Kruse
>> Sent: Thursday, January 11, 2007 2:38 AM
>> To: Athena mailing List
>> Subject: [Ifeffit] Projekt with the "flatten-problem"
>> 
>> Hi,
>> 
>> find attached an example with the "flatten-problem".
>> thanks a lot,
>> 
>> jens
>> 
>> 
>> 
>> 
>> "Hi,
>> 
>> I have a normalization problem with Athena. If I turn on the 
>"flatten"
>> option in the background removal section, Athena creates in some of
>the
>> normalized spectra a step in the pre-edge range.  How can I  get rid
>of
>> it?
>> 
>> Thanks,
>> 
>> jens"
>