Dear All, Greeting.This is Yu-Chuan. After struggling a long time, I just felt a little bit progress in the fitting program. However, there are still some questions confused me. 1. What's the meaning and purpose of "Fit Background" in Artemis? I know the backgound as "bare atom" in EXAFS theory. So, what kind of situation we need to use this function? 2. Is that possible for the Debye-Waller factor(sigma^2) be negative? Actually, I am not so sure about the physical meaning for that. Just know its a kind of thermal vibration. 3. Sometimes, The results obtained from Artemis seems not the same. Says, the guess parameters and uncertainties may be varied even if you input the same data for different time.Has anyone met this problem before? Sincerely yours, Yu-Chuan Lin Graduate Student and Reseach Assistant Kansas State University