Hi Bruce, The comments are very helpful to assure my data processing and for future experiments. Yes, all measurements were obtained in Dispersive EXAFS mode. As for i know (at least until my preparation time) the bulk sample (first one) doesn't contain the Hf impurities. However, i will double check that point.
Regards, Raj On Fri, May 29, 2015 at 7:00 PM, <ifeffit-requ...@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-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: Peak at short distance in FT - YbVO4 nanoparticles > (Bruce Ravel) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 29 May 2015 12:52:38 -0400 > From: Bruce Ravel <bra...@bnl.gov> > To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov> > Subject: Re: [Ifeffit] Peak at short distance in FT - YbVO4 > nanoparticles > Message-ID: <55689956.8040...@bnl.gov> > Content-Type: text/plain; charset=windows-1252; format=flowed > > On 05/29/2015 11:54 AM, Raj kumar wrote: > > Recently, i have performed EXAFS for YbVO4 bulk (prepared through > > sintering process) and nanoparticles (at room temperature). > > Nanoparticles were synthesized by co-precipitation technique and their > > EXAFS was measured by passing the prepared solution using peristaltic > > pump. After all subtraction (background and solvent), nanoparticles XAS > > data were recovered and processed for the fitting. After Fourier > > transform, it was observed that both nanoparticles posses an additional > > short peak (or shoulder) at about 1.2 A from bulk. Since the peak > > appears much closer to 1 A, i suspect this may due to artifact or bad > > background subtraction. Hence, i would like to know the way to eliminate > > this peak at short distance. > > Hi Raj, > > A few comments: > > 1. Your bulk sample (the first one in the list) may have a bit of Hf > in it it. It's hard to tell, but the mu(E) seems to be trending > upward right at the end of the data, which is the approximate edge > energy of Hf L3. I got a slightly better background removal by > changing the end of the spline range to 600. But this a minor > detail. The real story seems to be that .... > > 2. You data are pretty noisy. If you plot chi(R) out to 10 Angstroms > (which is, presumably, well beyond where you should expect to see > good signal in your data), you get a sense of how the level of > noise manifests itself in chi(R). To my eye, the peak/shoulder at > about 1.2 that you are asking about is of about the same size as > the level of noise in your data. > > You are asking how to get rid of a feature in the data that is > aesthetically unpleasing. I don't think that's the right question. > > Your data are what they are. Your data are noisy and measured over a > rather short energy range. That doesn't give you a lot of choices > about how aesthetically appealing you can make the Fourier transform > be. > > You seem to be operating Athena correctly and there aren't any magic > buttons that will make your short, noisy data longer or less noisy. I > don't see anything obviously wrong in how you are processing your data > and -- short of using PhotoShop ;) -- I don't see any defensible way of > making the feature at 1.2 go away. > > > > Am I correct in thinking that these data are measured in the > dispersive geometry? If so, my suggestion is to reconsider how you > make your samples. This kind of experiment is VERY sensitive to the > homogeneity of the sample. You have to take extraordinary care to make > your samples as homogeneous as possible. I suspect most of the > glitchy little points in your data are indicative of sample > inhomogeneity. > > You also should worry about purity of your source material. Granted, > it canbe very difficult to obtain rare earth metal samples that are > elementally pure. But if your data range is short because of other > edges, then you need samples that are more pure. > > HTH, > B > > > -- > Bruce Ravel ------------------------------------ bra...@bnl.gov > > National Institute of Standards and Technology > Synchrotron Science Group at NSLS-II > Building 535A > Upton NY, 11973 > > Homepage: http://bruceravel.github.io/home/ > Software: https://github.com/bruceravel > Demeter: http://bruceravel.github.io/demeter/ > > > ------------------------------ > > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > > End of Ifeffit Digest, Vol 147, Issue 20 > **************************************** >
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