A totally unrelated joke: If anyone ever watched "Da Ali G" show on HBO, there was an episode, when Ali G interviews a famous economics professor. The first question was: "Professor, what is a PIN code?" A. -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of Todd Luxton Sent: Tuesday, January 09, 2007 10:41 AM To: 'XAFS Analysis using Ifeffit' Subject: [Ifeffit] Is there a physical meaning to a negative SO2 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