Valerie, What type of energy range are you looking at? How far back do samples go?
Chris ********************************************** Dr Christopher Patridge Associate Professor Dept of Chemistry SASE 315 716-829-8096 | patri...@dyc.edu www.dyc.edu <http://www.dyc.edu/> Social: Twitter <http://www.twitter.com/drpatridgc> > On Mar 5, 2021, at 11:06 AM, Schoepfer, Valerie <valerie.schoep...@usask.ca> > wrote: > > Hi Matt, > > The backstory is that I'm trying to find which standards will define my > samples, so I am pulling standards from different beamlines and years to get > a basic linear combination fit, to run new standards myself when I have more > beamtime. > > I'm able to do it in Athena- where you more or less: > 1. Assign E0 to the first peak in the first derivative of your standard > reference foil. > 2. Calibrate one standard reference foil to the theoretical edge energy. > 3. Ensure E0 is right/adjust E0 for all samples and sample foils. > 4. Align reference foils to the standard reference foil, because the foil > will pull the sample with it. > > But in Larch, maybe I'm unsure about the groups function? I'm not convinced > the reference foils 'follow' the sample spectra. > If the reference and samples aren't tied together, how do you align samples > when your energies are off because of different beamlines or years or people > not as careful to calibrate the beamline energy? > My first thought was using the first derivative peak of your sample, but if > your edge energy shifts because of oxidation state changes, what do you use > then? > > > I'm still trying to form my question, so let me know if this still doesn't > make much sense. > Thanks! > Valerie > > > -----Original Message----- > From: Ifeffit <ifeffit-boun...@millenia.cars.aps.anl.gov> On Behalf Of > ifeffit-requ...@millenia.cars.aps.anl.gov > Sent: Thursday, March 4, 2021 12:00 PM > To: ifeffit@millenia.cars.aps.anl.gov > Subject: Ifeffit Digest, Vol 217, Issue 3 > > CAUTION: External to USask. Verify sender and use caution with links and > attachments. Forward suspicious emails to phish...@usask.ca > > > Send Ifeffit mailing list submissions to > ifeffit@millenia.cars.aps.anl.gov > > To subscribe or unsubscribe via the World Wide Web, visit > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > or, via email, send a message with subject or body 'help' to > ifeffit-requ...@millenia.cars.aps.anl.gov > > You can reach the person managing the list at > ifeffit-ow...@millenia.cars.aps.anl.gov > > When replying, please edit your Subject line so it is more specific than "Re: > Contents of Ifeffit digest..." > > > Today's Topics: > > 1. Re: Larch energy calibration (Matt Newville) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 3 Mar 2021 18:38:24 -0600 > From: Matt Newville <newvi...@cars.uchicago.edu> > To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> > Subject: Re: [Ifeffit] Larch energy calibration > Message-ID: > <ca+7esbrgytdjidl4x+rcuei+dfml3duyg-r2r-fhffeqshs...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Hi Valerie, > > On Tue, Mar 2, 2021 at 10:48 AM Schoepfer, Valerie < > valerie.schoep...@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 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20210303/99a209b2/attachment-0001.htm> > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > 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 > > > ------------------------------ > > End of Ifeffit Digest, Vol 217, Issue 3 > *************************************** > > _______________________________________________ > 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
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