Dear Bruce
Thanks a lot for your suggestion. Yes, I did according your suggestion. I did the self-absorption correction and got the perfect spectrum as shown below.
However, for the pure standards without dilution by BN, How to do the self-absorption correction? For example, I try one, but cannot get the credible spectra. For Dibenzyl Disulfide, the formula should be (C14H14S2)0.5435(BN)0, no dilution. I put (C14H14S2)0.5435(BN)0 in, but the spectrum I got is
So can you tell me how to do the pure standards self-absorption correction using Athena?
Much appreciated.
Warm regards
Juan Chen
At 2012-02-15 02:00:01,ifeffit-request@millenia.cars.aps.anl.gov wrote: >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-request@millenia.cars.aps.anl.gov > >You can reach the person managing the list at > ifeffit-owner@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: fitting sulphur using standards by Athena (Bruce Ravel) > 2. Re: fitting sulphur using standards by Athena (Matthew Marcus) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Tue, 14 Feb 2012 09:07:45 -0500 >From: Bruce Ravel <bravel@bnl.gov> >To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> >Subject: Re: [Ifeffit] fitting sulphur using standards by Athena >Message-ID: <201202140907.45529.bravel@bnl.gov> >Content-Type: Text/Plain; charset="utf-8" > >On Tuesday, February 14, 2012 07:55:54 am ?? wrote: >> As I known, the spectra for standard diluted with BN and non-diluted are >> different. The peak of the non-diluted is low due to self-absorption, as >> shown in the figure below. S1 is non-diluted and s1_10 is diluted sulphur >> to about 3%. For dilution, the position of the peak is also changed. >> Therefore the non-diluted s1 spectra isnot the real spectra of >> dibenzothiophene. The question is what percentage should I dilute the >> standard to get the credible spectra for the standards?and how to explain >> the peak position change? > >Although this sort of thing can be approximated from tables of >absorption coefficients, the advice I usually give to my users is to >prepare a series of samples of diminishing concetrations and measure >then. > >Having a good intuition for sample preparation and the effects of poor >sample preparation is always important and even more so for low energy >edges. The best way to develop that intuition is by doing the >experiment yourself. > >> Can I use Athena to counteract the self-absorption and get the >> credible spectra for sdandards? > >Yes it can -- in principle. Doing a good job of self absorption >correction requires a lot of knowledge about your sample and its >matrix -- often more than one has. > >The use of the self absorption tool is explained in the Athena >document. I have also written a lecture on this topic. Go to > > https://github.com/bruceravel/XAS-Education/downloads > >and download the "selfabs.pdf" file. > >B > > >-- > > Bruce Ravel ------------------------------------ bravel@bnl.gov > > National Institute of Standards and Technology > Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 > Building 535A > Upton NY, 11973 > > My homepage: http://xafs.org/BruceRavel > EXAFS software: http://cars9.uchicago.edu/ifeffit/Demeter > > > >------------------------------ > >Message: 2 >Date: Tue, 14 Feb 2012 07:33:38 -0800 >From: "Matthew Marcus" <mamarcus@lbl.gov> >To: "XAFS Analysis using Ifeffit" <ifeffit@millenia.cars.aps.anl.gov> >Subject: Re: [Ifeffit] fitting sulphur using standards by Athena >Message-ID: <03B21711433A40B4AA45C3DE3410452A@als.lbl.gov> >Content-Type: text/plain; format=flowed; charset="utf-8"; > reply-type=original > >To reiterate a point which is often not understood - dilution won't fix overabsorption if the particles of the concentrated material >which are mixed in with the diluent are too big. For concentrated S compounds, "too big" is in the low microns. >When I run a S standard, I do it in total electron yield to avoid this problem. When I fit a S spectrum, I use a crude >oveabsorption model with a single parameter which is treated as an unknown fitting parameter, with the assumption >that the reference spectra were collected in a way which avoids overabsorption. > mam >----- Original Message ----- >From: "Bruce Ravel" <bravel@bnl.gov> >To: "XAFS Analysis using Ifeffit" <ifeffit@millenia.cars.aps.anl.gov> >Sent: Tuesday, February 14, 2012 6:07 AM >Subject: Re: [Ifeffit] fitting sulphur using standards by Athena > > >> On Tuesday, February 14, 2012 07:55:54 am ?? wrote: >>> As I known, the spectra for standard diluted with BN and non-diluted are >>> different. The peak of the non-diluted is low due to self-absorption, as >>> shown in the figure below. S1 is non-diluted and s1_10 is diluted sulphur >>> to about 3%. For dilution, the position of the peak is also changed. >>> Therefore the non-diluted s1 spectra isnot the real spectra of >>> dibenzothiophene. The question is what percentage should I dilute the >>> standard to get the credible spectra for the standards?and how to explain >>> the peak position change? >> >> Although this sort of thing can be approximated from tables of >> absorption coefficients, the advice I usually give to my users is to >> prepare a series of samples of diminishing concetrations and measure >> then. >> >> Having a good intuition for sample preparation and the effects of poor >> sample preparation is always important and even more so for low energy >> edges. The best way to develop that intuition is by doing the >> experiment yourself. >> >>> Can I use Athena to counteract the self-absorption and get the >>> credible spectra for sdandards? >> >> Yes it can -- in principle. Doing a good job of self absorption >> correction requires a lot of knowledge about your sample and its >> matrix -- often more than one has. >> >> The use of the self absorption tool is explained in the Athena >> document. I have also written a lecture on this topic. Go to >> >> https://github.com/bruceravel/XAS-Education/downloads >> >> and download the "selfabs.pdf" file. >> >> B >> >> >> -- >> >> Bruce Ravel ------------------------------------ bravel@bnl.gov >> >> National Institute of Standards and Technology >> Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 >> Building 535A >> Upton NY, 11973 >> >> My homepage: http://xafs.org/BruceRavel >> EXAFS software: http://cars9.uchicago.edu/ifeffit/Demeter >> >> _______________________________________________ >> Ifeffit mailing list >> Ifeffit@millenia.cars.aps.anl.gov >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit >> > > > >------------------------------ > >_______________________________________________ >Ifeffit mailing list >Ifeffit@millenia.cars.aps.anl.gov >http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > >End of Ifeffit Digest, Vol 108, Issue 17 >****************************************