I am very new to XAFS analysis, I am wondering if there is a physical meaning to a negative value for SO2.  Based on the XAFS equation I can’t understand what the physical significance of a negative SO2 value would be, therefore I am assuming that my modeling results using Athena are not representative of a physically realistic model due to the negative value calculated fro SO2 or more specifically the amp variable in the guess set.  Any insight would be greatly appreciated.

thanks