Hi Matt, Thank you very much for your comments. S02 is a variable for me and it gives information about the size of the particles (related to coordination number). For instance, in the case of Pt foil it should be close to 0.85, however it is much smaller (0.20) in the case of platinum nanoparticles (size < 2nm), Anatoly commented that it is normal this low value in the case of nanoparticles. Probably, what you purposed it has more sense than what I did. Then, as I understand, I have to suppose reasonable value of S02, lets say 0.85, or shall I have to use S02 from Pt foil? Secondly, I define the variable amp = S02*N and, shall I write a value of one in the box corresponding to N? I mean, the sight in Artemis shows like this: N:1 X S02:amp.
Talking about the Nyquist theorem, a higher number of independent points implies a higher number of variables that can be used and it is especially useful for me when I fit only the first shell (R-range is small) due to the low number of independent points obtained. If I use the formula "+2", I can define more variables. I usually use the crude rule: number of variables < 2/3 Nip. I read this "+2" formula described by D.C. Koningsberger et al (Topics in Catalysis 10 (2000) 143-155) and I though that was ok. What is the origin of this "+2"? I have obtained a value of 0.53 for S02 in the case of Pt foil, it suggests (as people from this e-mailing list said) that a correction of self absorption should be used until reaching a reasonable value for S02 (0.85). After this, I will apply the same correction to the samples because they were measured in fluorescence way too. My samples contain less than 1% of platinum in weight (about 0.80%) and I do not know if there will be self-absorption. Finally, I would like to ask about the detection of low Z scatterers (usually O or C from the support). I read in the aforementioned paper the difference file technique, Artemis includes this possibility? How can low Z scatterers be detected? Thanks a lot Best regards, JA
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