Abhijeet,
Consider the energy resolution of the dispersive EXAFS
beamline. A poor energy resolution could suppress the low-k amplitude
causing the Debye-Waller factor to compensate by being articifically low.
However, you also have an amplitude larger than 1. Adding an Ei component
will address the problem of poor energy resolution, but I would suggest that it
should be based on the measured energy resolution rather than being a "guessed"
variable. You can also measure the appropriate Ei using a known sample,
such as a copper foil for which you have comparable spectra on a beamline with
better energy resolution.
What scattering paths and at what bond lengths are
responsible for the peak below 1 angstrom? It seems unlikely to me that a
Cu-O or Cu-N path would produce such a peak. These peaks would more
typically be closer to 1.5 angstroms.
Jeremy Kropf
Chemical Sciences and Engineering
Division
Argonne National Laboratory
Argonne, IL
Hi all,
I read the
discussion on negative Debye waller factor. As per the discussion the negative
value of this factor shows that the model has shortcomings, so it should be
corrected.
I am also getting the
same problem while fitting one of my samples. It is a Cu complex whose EXAFS
data is taken at Dispersive EXAFS beamline at RRCAT, Indore, India.
In the complex the
nearest neighbours of Copper atom are Nitrogen and Oxygen.
I am getting a very good fit
upto 3rd shell but the problem is that all ss parameters are coming negative.
I checked the model it seem correct.
Also I am getting a peak
below 1 Angs which is also getting fitted but I am not able to get that
whether it is a real or due to some noise.
I am attaching herewith the
results of data analysis and fitting.
Thanks in advance
With regards
Abhijeet Gaur
Vikram University
Ujjain, INDIA