Matt and Matthew, Thanks for your suggestions. I will try to collect some spectra well above the Co L-edge and see if they provide additional insight.
Best, George On Tue, Apr 1, 2014 at 6:07 PM, Matthew Marcus <mamar...@lbl.gov> wrote: > I don't think so. This may be a better question for M. Newville, or > whoever wrote the program. > mam > > > On 4/1/2014 9:56 AM, George Sterbinsky wrote: > >> Hi Matthew, >> >> Hephaestus shows the strength of the Ll emission to be about 10% of the >> La2 emission. When fitting the spectrum as a sum of Gaussians, I find that >> the area of of the Gaussian used to fit the Ll is 24% of that used to fit >> the La2. What would cause the ratio determined from tabulated data to >> differ from that found in the data I collected? Am I misunderstanding the >> meaning of the "strength" value in Hephaestus? >> >> Thanks, >> George >> >> >> On Tue, Apr 1, 2014 at 11:45 AM, Matthew Marcus <mamar...@lbl.gov<mailto: >> mamar...@lbl.gov>> wrote: >> >> OK, I think the "other Matt" has solved it - it's the L1 peak. I was >> confused by an inaccurate attempt at reading the energy scale. >> Also, I somehow didn't read correctly the branching ratio from >> Hephaestus. >> mam >> >> >> On 3/31/2014 8:57 PM, George Sterbinsky wrote: >> >> Hi Matt, >> >> Thanks for your reply. Please see below. >> >> On Mon, Mar 31, 2014 at 8:10 PM, Matt Newville < >> newvi...@cars.uchicago.edu <mailto:newvi...@cars.uchicago.edu> <mailto: >> newville@cars.__uchicago.edu <mailto:newvi...@cars.uchicago.edu>>> wrote: >> >> Hi George, >> >> Calibrated spectra would help, but if we guess the >> calibration is 0.56 >> bins/ eV, then we'd have >> >> >> I've attached a plot of the data showing the x-axis in keV. Also, >> as requested by Zack, I've attached a two column data file. >> >> >> line E (eV) bin # >> ------------------------------__--------------- >> >> Co La1,2 775 434 >> O Ka1,2 525 294 >> C Ka1,2 277 155 >> >> which looks pretty good. This puts the the unknown peak >> near >> 380/0.56 which is 678 eV. Tthat's very close to Co Ll >> (M1->L3), >> which is at 677 eV, and should be a bit less than 10% of Co >> La1 and >> La2, which is roughly right. >> >> >> Based on fitting the spectrum with Gaussians, the Co LI is 24% of >> the La2. As you mention, a value of roughly 10% is expected. What could >> cause such a discrepancy? >> >> >> So, I think it's Co Ll. That says the sample is just Co, C, >> and O. >> Is that reasonable? >> >> >> Yes, it is. I think maybe a little fluorine too, but it is very >> weak as I mention in my response to Matthew. >> >> >> What surprises me is that there is no signal from the >> elastic peak. >> Was that somehow filtered out? >> >> >> No, if there is an elastic peak it is probably lost under the Co >> La2. >> >> >> Thanks, >> George >> >> The fact that the counts don't go to >> zero between C and O could be many factors, including >> incomplete >> charge collection. This (and Compton scattering) generally >> make peaks >> have a slightly non-Gaussian shape, with a low-energy tail. >> >> >> >> >> >> >> Cheers, >> >> --Matt >> >> On Mon, Mar 31, 2014 at 5:01 PM, George Sterbinsky >> <GeorgeSterbinsky@u.__northwestern.edu <mailto: >> georgesterbin...@u.northwestern.edu> <mailto:GeorgeSterbinsky@u.__n >> orthwestern.edu <mailto:georgesterbin...@u.northwestern.edu>>> wrote: >> > Hello, >> > >> > I am writing with a general XAS question. It does not >> necessarily pertain to >> > Ifeffit, however, I think the topic is something some, >> maybe most, list >> > members will be knowledgeable about. So it seems like >> this list is a good >> > place to post this question. >> > >> > On to the question. I have attached a plot of a MCA >> spectrum collected with >> > a vortex silicon drift detector. The spectrum is actually >> the average of >> > several spectra, all collected in the post edge region of >> the Co L-edge. The >> > spectra were averaged to reduce noise. The three peaks >> result from >> > fluorescence from carbon, oxygen, and cobalt. Low-energy >> shoulders on the Co >> > and O peaks are also observed. These can be seen as the >> regions of the >> > spectrum that are not well reproduced by the fit. The >> main reason I included >> > the fit in the plot is to illustrate the presence of >> these shoulders, >> > particularly in the oxygen florescence, where the >> additional intensity is >> > not so obvious. >> > >> > I am writing to see if anyone has any suggestion as to >> what the origins of >> > these peaks might be. They are not due to additional >> elements, as they >> > appear at the same incident energies as the main >> florescence peaks, i.e. the >> > Co shoulder appears at the same incident energies as the >> main Co peak, and >> > the O shoulder appears at the same incident energies as >> the main O peak. It >> > is possible that the peaks result form other transitions. >> Considering Co, >> > the main peak is due to L3/L2-M4 transitions, and the >> shoulder is in a >> > position that could be consistent with L3/L2-M1 >> transitions. However, by >> > fitting the peaks with Gaussians, one finds an area for >> the shoulder that is >> > about 25% of the area of the main peak. This is >> significantly larger than >> > what one might expect from tabulated transition strengths >> like those given >> > in Hephaestus. >> > >> > To summarize, does anyone know what these shoulders might >> result from if not >> > lower energy transitions? If they are low energy >> transitions, why would the >> > relative transition strengths differ from tabulated >> values? >> > >> > Thank you, >> > George >> > >> > >> > >> > >> > _________________________________________________ >> > Ifeffit mailing list >> > ifef...@millenia.cars.aps.anl.__gov <mailto: >> Ifeffit@millenia.cars.aps.anl.gov> <mailto:ifef...@millenia.cars.__ >> aps.anl.gov <mailto:Ifeffit@millenia.cars.aps.anl.gov>> >> > http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit >> <http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >> > >> >> >> >> -- >> --Matt Newville <newville at cars.uchicago.edu < >> http://cars.uchicago.edu> <http://cars.uchicago.edu>> 630-252-0431 <tel: >> 630-252-0431> <tel:630-252-0431 <tel:630-252-0431>> >> _________________________________________________ >> Ifeffit mailing list >> ifef...@millenia.cars.aps.anl.__gov <mailto: >> Ifeffit@millenia.cars.aps.anl.gov> <mailto:ifef...@millenia.cars.__ >> aps.anl.gov <mailto:Ifeffit@millenia.cars.aps.anl.gov>> >> http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit < >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >> >> >> >> >> >> _________________________________________________ >> Ifeffit mailing list >> ifef...@millenia.cars.aps.anl.__gov <mailto: >> Ifeffit@millenia.cars.aps.anl.gov> >> http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit < >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >> >> _________________________________________________ >> Ifeffit mailing list >> ifef...@millenia.cars.aps.anl.__gov <mailto:ifef...@millenia.cars. >> aps.anl.gov> >> http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit < >> 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 >> >> _______________________________________________ > 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