Hi Bindu: On Sun, 2 Dec 2007, Ravel, Bruce wrote:
The EXAFS equation is:
N S02 F(K) chi(k) = ----------- exp(-2k^2 sigma^2) sin(2kR + phi(k)) 2kR^2
In the oscillatory term, there is a piece that is the phase shift associated with the scattering of the photoelectron. When you do a Fourier transform, the peak of the sin wave is not at R, rather it is shifted by an amount that depends on the size of phi(k).
In addition, because this is a sum of sinusoids with different phases, will not necessarily result in a single, distinct peak. Interference effects are quite common. Carlo -- Carlo U. Segre -- Professor of Physics Associate Dean for Special Projects, Graduate College Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://www.iit.edu/~segre segre@debian.org