On Tue, Feb 28, 2017 at 9:48 AM, Bruce Ravel
On 02/28/2017 10:10 AM, Samy Ould-Chikh wrote:
Dear Ifeffit mailing list,
I have a question which concern units and I can’t find the answer in the Feff manual.
In a FeffNNN.dat output file, what are the unit of the numbers (if any) corresponding to
φc,
|Feff|,
φeff,
the reduction factor,
λ,
Re(p)
Samy,
This is a peculiar reference, but I think the clearest written explanation of this is in the manual for the ancient "feffit" program. Here is a copy of its manual:
http://cars.uchicago.edu/~newville/feffit/feffit.pdf
You will want to look at page 22. While the rest of the manual is not so useful anymore (in the sense that there are very few users of the old feffit remaining), it's explanation of how the feffNNNN.dat files are used is excellent.
Eq. 6.1 should clarify how each term is used and what the units are. Column 1 is, of course, inverse Angstroms. Columns 2, 3, and 4 are unitless. The two phase terms go into the argument of the sine, thus must be unitless. The amplitude term is multiplied by N and S02, thus is also unitless. The reduction factor, as well, is unitless -- it is used in the computation of the amplitude term in equation 6.1.
Lambda has units of angstroms, the real part of p (which is the complex wavenumber used in the Feff calculation) has units of inverse Angstrom.
I am pretty certain I got all that right.
I think it would be a good idea to capture all of this information as well as eq. 6.1 in the Artemis manual.
HTH, B
Yes, the units for the data in the columns are: mag[feff] and red factor: unitless terms for amplitude real[2*phc] and phase[feff]: radians k, real[p]: inverse Ang lambda: Ang See http://cars.uchicago.edu/xraylarch/xafs/feffpaths.html and http://cars.uchicago.edu/xraylarch/xafs/feffpaths.html#the-exafs-equation-us... --Matt