Hi Kefan, I'll risk some comments here since I've worked with Ge nanocrystals before. Keep in mind that these are comments based on the belief you measured at a synchrotron facility (essential when working with nanostructures, I guess) and on the information you gave, which does not mention how dilute your samples are, if you measured in transmission or fluorescence mode, if the samples are solely composed of Ge or not (and they are very likely not to be - is there any Si in your samples?), if there is a matrix around the QDs or if they are in solution with surfactant atoms, ect. Such circumstances might make my comments dubious (or even more dubious), but I'm sure more experienced users would warn you should that happen. 1 - The first thing I noticed when opening your project is that you do not have any standards! You should have at least one bulk crystalline Ge standard when working with Ge nanostructures. Having bulk amorphous Ge and bulk GeO or GeO2 standards would also be very useful. Just by comparing the spectra of your QDs to the spectra of the bulk standards (check the attached project) we can infer that your QDs are very unlike to be crystalline like bulk Ge, even after annealing. You can tell this by the complete lack of oscillations at higher k in your spectra (from k ~ 8 inverse angstrom onwards the signal looks like noise-only). In fact, even the amorphous Ge standard has more oscillations at higher k. Further evidence is given by the XANES structure after the white line, which does not resemble either crystalline or amorphous bulk Ge. And it does not resemble the bulk crystalline oxide as well. I know this was not your question but I mention it here to warn you that your data goes against the assumption that you have "elemental Ge QDs"; it actually suggests that you have "Ge-something QDs". 2 - You surely have an awful lot of glitches (sharp spikes) in the spectra with higher numbers (i.e., Ge23, Ge24, etc), which I assume to be the QDs annealed at the highest temperatures. Interestingly, the glitches do not appear always in the same places, so I'd guess that they are not originated from harmonic reflections or monochromator issues. They might be related to the sample preparation method; Grant Bunker has elaborated a very good presentation on EXAFS sample preparation that you can check at http://gbxafs.iit.edu/training/XAFS_sample_prep.pdf . It might be of help for future measurements. As for your spectra now, I guess you can try and deglitch them. Deglitching in Athena is easy, as you can verify in the Athena manual (the one you mentioned a few days ago). Keep in mind that when deglitching you should remove the sharp spikes without changing the oscillatory features in your spectra. Nevertheless, it seems to me that even after deglitching it will be pointless to try and fit something beyond k ~ 10 inverse angstrom. Good luck, anyways. 3 - Finally, I'd advise you (since you asked for advice ;) ) to mind the title of future emails. "Give me some advice" does not sound well in English, I guess. It sounds like giving and order, which I believe (and hope) was not your intention. A "Please" at the begging (or end) would help making people more prone to help you... Hope all this babbling helps, Leandro On Dec 17, 2007 9:22 PM, wrote:

Hi I have used the Athena 0.8.054 to processing the EXAFS data of Ge quantum dots. You can find the .prj file in the attachment. In fact, they are a seriers of samples with or without annealing at high temperature. Surely, the data after annealing is difficult to deal with. Please do not hesitate to give me some advices! Such as the issues on normalization, deglitching, truncating, etc. Thanks a lot.

PS, I think this is a good way to exchange experiences and learn knowledges. Kefan -- Kefan Wang School of Physics and Electronics Henan University, 475004 E-mail: kfwang@henu.edu.cn; wang.kefan@gmail.com _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit