I am analysing exafs spectra of some heavy metal compounds. I tried exafs fititng for compounds in artemis but not getting final parameters in permissible range and not even proper fit for some compounds. Then, I moved to wavelet transform of that data and got good contour graphs. I have questions
1. what parameters can be evaluated from these WT plots and these graphs are alone sufficient for justification (without exafs fitting in artemis)?
2. In wavelet transform graph, first neighbour atom contour centroid showing neighbour distances at low R values in all compounds but if I am applying a certain shift then all distances will shifted to correct values. Is there any any kind of shift we can apply or how?
Dear Harpreet Singh ,
I must apologize that I am not familiar yet with 'artemis' and the wavelet approach.
But as far as I remember from our early EXAFS evaluations, there is the parameter Eo, which is used as the origin (zero) of the kinetic energy scale of the emerging photo-electron. From that scale the k-scale of the EXAFS is derived... and a change delta_Eo of Eo will affect that k-scale, the phases and also the R-values, which are hidden in the EXAFS periodicity (wave-length) in k-scale.
That delta_Eo is different for different compounds*).
I do not know how the delta_Eo parameter is handled within artemis or your data evaluation.
Please have a look at that issue...
*) see for example:
Article Improved extended-x-ray-absorption fine-structure (EXAFS) st...
If neccessary, please ask for the full-text...
You may ask Dirk Luetzenkirchen-Hecht
(https://www.researchgate.net/profile/Dirk-Luetzenkirchen-Hecht).
He is still active in the EXAFS field and is more familiar with the modern EXAFS evaluation techniques and tools...
Best regards
G.M.
Gerhard Martens Thank you sir for your kind response. I have evaluated that E0 values for compounds by taking first derivative maxima of normalized mu spectra (i,e. XANES analysis part). I am facing problem in fitting of exafs spectra. I will check the recommended material mentioned by you.
Wavelet transform (WT) plots of EXAFS spectra can provide valuable insights into local atomic structures, but they have limitations compared to EXAFS fitting.
* Parameters from WT plots:
* WT can reveal the number of neighboring atoms around the absorbing atom and their relative distances (R-values). However, it often lacks precision in determining coordination numbers and Debye-Waller factors compared to EXAFS fitting.
* Shifting WT plots:
* Centroids in WT plots may not always correspond to exact R-values due to various factors. Applying a universal shift might not be ideal as the shift value can vary depending on the specific element and compound.
Hussein A. Jasim Thank you, sir, for providing insights into this discussion.
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