Hi Valerie,

On Tue, Mar 2, 2021 at 10:48 AM Schoepfer, Valerie <valerie.schoepfer@usask.ca> wrote:

Hi,

 

I am using Larch XAS Viewer for the first time to analyze some Mo XANES data. It is fairly straightforward, however I am running into problems with energy calibration, which leads to problems with Linear Combination Fitting.

 

Right now, which is likely wrong, I’m calibrating the energy of a standard to the theoretical edge, then auto-aligning the samples to the standard. But how do reference foils fit in here? Reference foils don’t seem to be tied to the sample like they are in Athena. Should I be manually aligning?

 

Is there a general guidance or work flow?


It's possible that I do not fully understand the question or that this answer will veer a bit off the topic of your question.

For sure, energies need to be aligned properly for any multi-spectra comparison or linear method to work well. But it should be that you will have groups of spectra that all share a consistent energy calibration, say from the same beamline/beamtime. 

If you do have a reference channel for every measurement, you can compare those reference channels.  Ideally, these will not vary for every measurement - that would indicate a serious problem.   So, I think you should be able to group spectra together as uniformly calibrated (hopefully all data from a day or more of beamtime at a particular beamline) and then make sure that the different groups of spectra.  Does that seem reasonable? 

I have to admit that at my beamline I don't often have the luxury or need to run a reference foil for every scan, so we calibrate consistently ahead of time.  I'm sure that leads to a bias in the software.   I guess I forgot that Athena had the ability to read and tie a second spectrum as a "reference" and use that to auto-apply calibration.   

Is it generally necessary to calibrate many spectra individually, or do people find that doing them in a few large groups is sufficient?

--Matt