[Ifeffit] Filter window shape for FT?

[Matthew Marcus]

This is about going to what you guys call q-space.  It's often of interest to be able to display the contributions from specific 
shells,
thus showing off such things as beat-nodes.  For instance, in phyllomanganates, the Mn-O first shell is often not of great interest, 
but
the split Mn-Mn second shell is.
    mam
----- Original Message ----- 
From: "Scott Calvin" <SCalvin at slc.edu>
To: "XAFS Analysis using Ifeffit" <ifeffit at millenia.cars.aps.anl.gov>
Cc: <SCalvin at slc.edu>
Sent: Thursday, September 28, 2006 9:48 AM
Subject: Re: [Ifeffit] Filter window shape for FT?


> Just to clarify...do you mean you're doing the fits in q-space (i.e. the back transform)? Or do you actually mean that the window 
> used in k-space to get to R-space shouldn't have sharp corners? After all, if you're fitting in R-space, Artemis doesn't use an 
> R-space window per se, just a fitting range.
>
> --Scott Calvin
> Sarah Lawrence College
>
> At 12:36 PM 9/28/2006, you wrote:
>>I've always been told that when doing Fourier filtering, the R-space window shouldn't have sharp corners.  Artemis, for instance, 
>>allows you
>>to vary this, and by default puts shoulders on the window.  I have  a user who now wants the sharp corners, claiming that it 
>>provides the best
>>filtering.  He describes this as "doing the FT in a region of R-space".  What does the Assembled Multitude think of the risk of 
>>termination
>>effects with a rectangular window?
>>    mam
>
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