[Ifeffit] EXAFS data

[Carlo Segre]

Hi Abhijeet:

The Farrel Lytle data is in the form of staps with calibration points. 
You need to make a conversion to energy.  Grant Bunker sent me this 
description a while ago.  I have written a Python program to do the 
conversion but have had no time to finish it off and make it really 
useful.

Hope this helps

carlo

--------------------------------------------------------------

>From bunker at iit.edu Wed Aug  6 12:27:28 2008
Date: Wed, 6 Aug 2008 12:27:13 -0500
From: grant bunker <bunker at iit.edu>
To: segre at agni.phys.iit.edu
Subject: Re: Lytle database

I wrote a little conversion program in mathematica for  somebody who 
asked a year or so ago.  It should be easy to pythonize it.  The main 
thing to remember is the first column is in motor steps (!), and the 
angle is a linear function of motor steps, and the rest is just 
Bragg's law. Things are referenced physically to the copper edge.

Key parameters used in the data acquisition program are in the header: 
dspace is obvious, stepdeg is steps per degree in the mono, cuedge is 
the position of the Cu edge as measured in motor step units.

So, the business end of the conversion is something like this:

(*constants*)
hc=12398.5;
Cuenrg=8980.3;

(* these things should be extracted from file header *)
dspace=3.13562;
cuedge=50880.;
stpdeg=4000.;

(* code*)
const=hc/(2*dspace);
thetaCu=ArcSin[const/Cuenrg];
theta[n_]:=(n-cuedge)/stpdeg*pi/180.+thetaCu
e[n_]:=const/Sin[theta[n]]


I'm not positive, but I think the channel offsets are already 
subtracted from the other columns; the offsets are just listed for 
documentation.

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On Wed, 28 Jan 2009, abhijeet gaur wrote:

> Hi
>     We have Farell Lytle type data. When we put that into ATHENA we get the
> Energy curve. But we are not able to extract that Energy converted data from
> ATHENA . We tried to import the data in ORIGIN but we could not do so though
> the graph was imported.So if there is any way to extract the data please let
> us know.
>
> Thanks
>
> Abhijeet
>

-- 
Carlo U. Segre -- Professor of Physics
Associate Dean for Special Projects, Graduate College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://www.iit.edu/~segre   segre at debian.org