Hi Matt, On Wed, May 12, 2004 at 01:41:49PM -0500, Matt Newville wrote:
But to do the self-absorption corrections on a well-characterized sample, you can use tabulated cross-sections (using barns/atoms is HIGHLY recommended over cm^2/gr or cm^-1 unless you have a pure compound: densities do not add!), and scale the XAFS wiggles to the edge jump of the absorbing atom. That assumes that the tabulated value for mu are correct except that they ignore the XAFS.
Ok, this is what I normally do "by hand". The first part of my question - if this is right - has been widely answered by you and Tsu-Chien. The second part concerned if someone has already written a routine that can match the tabulated cross-sections and the XAFS one automatically and then write out a file containing the scaled XAFS.
I'm not sure I understand 'standing-wave-assisted EXAFS'. I'd interpret this to mean the measurements are done near the critical angle to control the penetration depth. Is that right? If so, and if you're asking for advice on self-absorption corrections, you'd need to give more details layer thickness, and measurement geometry.
Yes, you are right. For standing-wave-assisted EXAFS I mean fluorescence
measurements done at gracing-incidence. In multilayers a standing wave field
occurs for reflection at the first Bragg reflection order, so a defined
shift of the standing wave field position leads to different weights of
absorption.
The experimental setup is phi+theta=90deg with a Ge detector (13 elements),
incidence angle (theta) in the range 0.400-0.700deg. Samples are 10-periods
multilayers with the following structure:
SiO_2(15A)/[Si(42A)/Mo(28A)]_10/Si_substrate
I would like to simulate (and then correct) the selfabsorption in these
samples but applying the standard formula doesn't work. In my opinion, I
think that this is due to the fact that the field intensity in the sample is
not exponentially decaying but oscillating+exponentially-decaying (because
it is a standing wave field).
Thanks,
Mauro
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Mauro Rovezzi