Hi Pei-chang, Regarding questions 1 and 2: Go to http://xafs.org/Tutorials and read Matt Newville's "The Fundamentals of XAFS". Regarding question 3 - 5: On that same page, Matt's and Shelly's tutorials cover that information. This part of the Athena document is also relevant: http://cars9.uchicago.edu/~ravel/software/doc/Athena/html/bkg/rbkg.html HTH, B -- Bruce Ravel ----------------------------------- bravel@bnl.gov My homepage: http://cars9.uchicago.edu/~ravel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/ -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of ?? ? Sent: Tue 10/2/2007 8:56 AM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] The common question! To Dear Authors; We have accumulate some questions on attach ptt.file, that including theoretical and athena background removal file. In order to present our questions more clear and short, we make this way, Thanks for your time and help! Pei-chang Tsai ??????,?????? - ???? Yahoo!??????!