[Ifeffit] Athena plotting multiple k-weights; confusion about "k" and "k-weight"

Kelly, Shelly D. SKelly at anl.gov
Mon Aug 15 13:44:26 CDT 2005

```Hi Charles,

I think that you understand correctly and that Athena doesn't label the axis correctly when multiple k-weights are being plotted.  The FT are different when different k-weights are used because different regions of chi(k) are emphasized differently.

Shelly

-----Original Message-----
From: ifeffit-bounces at millenia.cars.aps.anl.gov on behalf of Charles Chusuei
Sent: Mon 8/15/2005 12:23 PM
To: 'XAFS Analysis using Ifeffit'
Subject: [Ifeffit] Athena plotting multiple k-weights; confusion about "k" and "k-weight"

Hello all:
I'm confused about what is meant by "k-weight" and "k" and how they are
used in the Athena plotting.  As I understand it, "k" refers to the
photo-electron wavenumber, k = [2m(E-E0)]/(h/2pi)^2]^ 0.5.  A "k-weight" is
the degree that chi(k) can be amplified.  For instance k-weight of "2" in
the Athena program plots a k^2*chi(k) versus k. A k-weight of "3" plots a
k^3*chi(k) versus k, etc.

However, in plotting multiple "spectra" using the same data file of
different k-weighting one can see the different lineshapes for each
k-weight [for instance assigning k-weights = 1,2 and 3].  Yet, the Athena
output has the labels of "k^2*chi(k)" versus "k" even though there are
multiple k-weights used.

Is this a typo in the ordinate label where it would be more appropriately
labeled as "k^n*chi(k)" versus "k" where n = weight, or am I fundamentally
misunderstanding the relationship between "k" and "k-weight"?  I'd
appreciate assistance in understanding if the latter is the case.