On 04/01/2016 07:58 AM, Matteo Busi wrote:

Now for my master thesis, I'm performing a correction to chi(E) in the E space regarding to some geometrical properties of the sample. I have also tried to re-import the corrected data as a chi(k), having reproduced the right k grid column, but it looks totally wrong. The thing I'm not sure about is if the chi(E) needs to be fourier trasnformed into chi(k) or not. That's because I would have liked to make comparison in the Athena software between the two chis, but if that's not possible I will keep it to the external software (mathematic) with which the correction is performed. Or if you can share me the fourier transform routine performed I can include it to my correction script.

You seem to be thinking about this wrongly. The chi(E) that gets written to the mu(E) ascii file using the thing we discussed last time is mu(E) - bkg(E) That's it. The difference between the chi(E) in the mu(E) file and the normal chi(k) is that (mu(E)-bkg(E)) is interpolated onto a uniform k-grid. There are at least two reasons for doing that, (1) every data sets then ends up on the same k-grid, which is a convenience, and (2) a uniform k-grid allows use of a /fast/ Fourier transform. If you want to overplot chi(E) and chi(k), you also have to do the coordinate transform between energy and wave-number, which depends upon the value of E0. You have never clearly explained what you are up to and why interpolating the normal chi(k) back onto the energy grid was inadequate, so I don't know what else I can say that would be helpful. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Building 535A Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/