Dear Feng,
On 6/28/07, Feng Wang
Thank you, Dr. Ravel,
Could you please just simply tell me the expression for the magnitude of chi (q) (labelled as |chi(q)|)? Thank you.
I'm sure you didn't mean to sound so demanding, but perhaps you would consider following Bruce's suggestion of sending a project file. For what it's worth (in case you missed it while you were reading the docs and tutorials), |chi(q)| = magnitude of the complex chi(q) = FT^(-1) [ chi(R) * Window(R) ] where Window(R) is a Windowing function and chi(R) = FT[ chi(k) * k^w * Window(k) ] where Window(k) is a Windowing function and w is the k-weighting. Both FT's are band-limited (Rmin,Rmax, and kmin,kmax, respectively). The convention used in Ifeffit is that chi(k) is strictly real. This isn't particularly important if you're only interested in the magnitude. I thought your original question was about scattering amplitudes.... Are these questions related? I couldn't tell much from the plot you sent, as I didn't understand what "X Axis Title" or "Y Axis Title" were meant to represent. Of course, the "scattering amplitude" f(k) is not the only factor setting the amplitude of chi(k). Hope that helps. If not, please let us know what the issue is, --Matt