[Ifeffit] phase shift correction

[Carlo Segre]

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 at iit.edu   http://www.iit.edu/~segre   segre at debian.org