Dear Bruce and Carlo,
Thank you very much for your reply.
Now I understand how Athena find the peak position by the Bruce's answer.
I think some kinds of interpolation is made when Athena find the white
line position because the peak position that Athena tells seems to be
more precise than the energy step in the measurement. Is that right?
Actually, I use this function often because it is quite useful for quick
check for white line position. But I will be careful when I use it from
now on, following the Bruce' advice.
I agree with the Carlo's suggestion that it is better to use the
curve-fitting method to find the white line position.
Best regards,
Hiroshi
Date: Thu, 2 Aug 2018 09:48:02 -0500 (CDT)
From: Carlo Segre
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Find white line position
Message-ID:
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Hiroshi,
You are probably better off putting a bit more time into the analysis and
simply fitting with an arctangent and a gaussian to get the white line
position.
Carlo
On Thu, 2 Aug 2018, Bruce Ravel wrote:
It's not very sophisticated.
Starting with the "flattened" spectrum (see
http://bruceravel.github.io/demeter/documents/Athena/bkg/norm.html#the-flattening-algorithm),
it simply finds the highest point in the spectrum. Literally just the
ceiling function.
The flattened spectrum is used rather than the normalized spectrum because
the curvature of the post-edge (or even the curvature of the pre-edge in
fluorescence data with a energy dispersive detector) could result in other
regions being higher in value than the white line.
This is a pretty horrible algorithm. It is, I think, guaranteed to find an
obviously wrong point for a metal. Basically it works for spectra with a
white line and it will almost certainly fail for spectra without a white
line.
Use with caution!
HTH,
B
On 08/02/2018 01:28 AM, Hiroshi OJI wrote:
Dear all,
I have a question about one of the useful function, "find white line
position" in Athena.
Could anyone tell me how Athena find the white line position by this
function? In other words, I would like to know the algorithm to find the
white line position in Athena.
Thank you very much for your help, in advance.
Best regards,
Hiroshi Oji
--
Carlo U. Segre -- Duchossois Leadership Professor of Physics
Interim Chair, Department of Chemistry
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498Fax: 312.567.3494
se...@iit.edu http://phys.iit.edu/~segre se...@debian.org
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