HI! You are new to XAFS? Welcome to the community. Many of the synchrotron facilities host courses annually on how to collect and analyze data. It can be very helpful to participate in one of these. There are also resources (tutorials) online
ZjQcmQRYFpfptBannerStart
This Message Is From an External Sender
This message came from outside your organization.
 
ZjQcmQRYFpfptBannerEnd
HI!
You are new to XAFS? Welcome to the community. Many of the synchrotron facilities host
courses annually on how to collect and analyze data. It can be very helpful to participate in one
of these. There are also resources (tutorials) online that can help you gain a better understanding
of the technique...e.g. https://xrayabsorption.org/

With regards to your particular problem, LARCH's choice of E0 is not unreasonable. What matters
most is that you are consistent in how you process your data. The E0 value is somewhat arbitrary
as it is intended to represent the onset of absorption, but structure in the edge can complicate that.
When fitting, there is a parameter used (deltaE0) to correct for discrepancies between the choice of
E0 and the calculated Fermi level.

A further idea to consider is how low in photo-electron momentum is usable in EXAFS. For your data,
and in general, data going down an edge is not well-fit to a background and is not going to be used
(and heavily suppressed by k-weighting when fitting). You don't have to take the spline to k=0 (i.e. to E0).
For your data, I would probably stop at around 9020 eV and not use below 9040 when transforming
and fitting.

Check the literature on how others have handled similar compounds. Again, what matters most is that
your choices for processing be reasonable and consistent.

cheers,
-R.

On 2024-05-13 7:08 p.m., Jan-Benedikt Weiss wrote:
Dear all, since I am new to XAFS analysis, I do not have a proper understanding of how to chose E0 the right way if taking the first maximum of the derivative of µ(E) is not an option. In my dataset (K-edge of a Cu(I) coordination polymer with
ZjQcmQRYFpfptBannerStart
This Message Is From an External Sender
This message came from outside your organization.
 
ZjQcmQRYFpfptBannerEnd
Dear all,

since I am new to XAFS analysis, I do not have a proper understanding of 
how to chose E0 the right way if taking the first maximum of the 
derivative of µ(E) is not an option. In my dataset (K-edge of a Cu(I) 
coordination polymer with linear coordination environment), a huge 
pre-peak far up the edge is present. Larch automatically detects E0 to 
be in front of that peak which leads to a complicated subtraction of the 
background in the EXAFS analysis (the spline does not align with the 
shape of the edge; see attached plot) and will probably lead to other 
problems. I thought of two alternative option to determine E0 but I do 
not know if they are adequate.

Option 1: Take the second maximum of the derivative of µ(E) which 
appears after the pre-peak (see attached plot). I guess this value is 
still flawed by the pre-peak and therefore not accurate.

Option 2: Fitting a baseline curve under the pre-peak and select E0 as 
the maximum of the derivative of that curve. Since this value will 
probably lay underneath the pre-peak, it will not be suitable as the E0 
value used in the background subtraction in the EXAFS analysis.

So do you have any suggestion on how to handle this case?

Best wishes
Jan

_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit