Find white line position
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 -- Hiroshi Oji, PhD. NUSR & AichiSR, Japan E-mail: h.oji@nusr.nagoya-u.ac.jp
It's not very sophisticated. Starting with the "flattened" spectrum (see http://bruceravel.github.io/demeter/documents/Athena/bkg/norm.html#the-flatt...), 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
-- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Lead Beamline Scientist, 06BM (BMM) Building 743, Room 114 Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Beamline: https://www.bnl.gov/ps/beamlines/beamline.php?r=6-BM Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/
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-flatt...), 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: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org
participants (3)
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Bruce Ravel -
Carlo Segre -
Hiroshi OJI