Dear all, I was so glad that Bruce and Zajac gave me advice about MS path treatment in last time. Thank you very much. Now, I am working on analysis of Cu K edge by using EDG_FIT, following previous papers. I am wondering if someone gave me comment about current problem for me. And my question about XANES analysis is "what the reasonable arc-tan is as a back ground of XANES." In previous some papers, Cu K edge were deconvoluted by assuming arc-tan edge jump function. But I couldn't found the reasonable mention for the shape of arc-tan. For example of Cu(II), one paper (1), which has interest in the metalloproteins active site, the arc-tan were positioned around 8992 eV with 5 eV hwhm approximatly. 　 But in another paper (2), which reported about high valence Cu(III), the arc-tan for Cu(II) complex looks having narrow hwhm at higher positons (around at 8984 eV). (1) /J. Phys. Chem./ B 2000, 104,10814-10819 (2) /JACS/ 2000, 122, 5775-5787 Are there any reason which can explain these difference? I hope any comment and advice. Takahide