Hi Bindu,
On Mon, Jan 26, 2009 at 8:28 AM, Bindu R.
I have one doubt regarding the measurement uncertainty in R- space (εR). In the manual it is written that εR is evaluated from the rms value of FT in the range 15-20 Å. My doubt is.....
In case the FT in R-space does not extend up to the range mentioned above, then how does the fitting program choose the value of εR?
The FT transform from k to R space that ifeffit does always extends to R = 10*pi Ang. The R-range saved into a data array is usually much shorter (it's usually out to 10Ang), though you can change this if you'd like. There are always high-frequency components of a real XAFS spectra. Anyway, when doing a fit, the data is FT to R-space internally, and the range between 15 and 20 Ang is used to estimate epsilon_R. Knowing the FT parameters (especially the k-weight), that can be converted into epsilon_k. --Matt