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://urldefense.us/v3/__https://xrayabsorption.org/__;!!G_uCfscf7eWS!bCIz... 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
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