Hi all I have a question regarding noisy EXAFS, since I analyze biological zinc samples. I have seen Bruce�s data and it is quiet as a sleeping snail all the way till chi(k)=16, however I have a completely different situation since I encounter noise at high chi(k) and I need an advice from whoever can supply it. As I use AUTOBK with emax set to maximum I observe chi(k) which is quiet at 0-9, and at 9-12 I obsrerve clearly the oscillations but with the addition of small spikes resulting from noise. At chi (R ) I see the first shell peak at 1.5A with amplitude of 1. Adjacent to this peak I observe a small peak at 1A with 0.5 amplitude. As I change Rbkg and Knin I cannot get rid of the small peak; the left region of the small peak is situated between 0.5 to 1A at chi(R ), and my attempts to keep this region �clean� failed. However, if I lower emax to 400, corresponding to approx. 10 at chi(K), and fourier-transform the region between 2 to 9 (the quiet region), the small peak disappears and the region at Chi (R ) between 0 to 1A is �clean�, but since I utilize less information the peaks at chi (R ) have lower resolution. My questions are: 1. What is the source of the small peak ? 2. Is it a real contribution from scattering ligands ? 3. How should I treat the small peak. 4. Should I get rid of it by all means ? if so, how ? My confusion arises from the fact that AUTOBK should get rid of atomic exafs at chi(k), consequently, the contributions at chi (R ) between 0 to 1A should get lower. In my case it seems that this contribution is lower, but it still exist with half the amplitude of the first shell peak. Any help would be appreciated. Thanks. Gabi. __________________________________ Do you Yahoo!? Yahoo! Photos: High-quality 4x6 digital prints for 25� http://photos.yahoo.com/ph/print_splash