Scott may be right about its borrowing. The term self-absorption is
used in XRF and XRD to describe the fall-off in characteristic line
emission from an x-ray tube with a heavy element (e.g. silver or
tungsten) target as the potential is increased. With light element
targets the emission increases roughly monotonically with potential.
With heavy element targets, the emission eventually saturates and may
even roll-over. See Quantitative X-ray Spectrometry, Jenkins, Gould
and Geddke, 1981.
Carl
Carl W. Ponader Ph.D.
Characterization Science Services
Corning Incorporated
SP-AR-2-4
Corning, NY 14831
607-974-3364
-Original Message-
From: ifeffit-boun...@millenia.cars.aps.anl.gov
[mailto:ifeffit-boun...@millenia.cars.aps.anl.gov] On Behalf Of Scott
Calvin
Sent: Tuesday, November 16, 2010 2:02 PM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Origin of terminology self-absorption
I tried a few searches, but rapidly get lost in other uses of the
term. My guess is we borrowed it from some other spectroscopy, much
the way we borrowed Debye-Waller factor from XRD, and then proceeded
to change its meaning. But it would be nice to be able to track that
down.
--Scott Calvin
Faculty at Sarah Lawrence College
Currently on sabbatical at Stanford Synchrotron Radiation Laboratory
On Nov 16, 2010, at 10:54 AM, Matthew Marcus wrote:
It's definitely a misnomer. I use overabsorption and encourage
others to do so. I suppose to track it down would require going
back over the seminal papers on the subject.
mam
On 11/16/2010 10:19 AM, Scott Calvin wrote:
Hi all,
As some of you know, I'm currently working on a textbook on XAFS
analysis. Because of that, I'm going to occasionally pose some
questions for the list that may seem a bit random. I hope none of
you mind me using the list in this way; the questions may seem to
come out of left field, but I think they will still be of interest
to many.
With that said, here's my question for today:
What is the origin of the use of self-absorption to describe the
suppression of fine-structure observed in thick, concentrated
samples measured in fluorescence? I understand the physics of the
effect itself, my question is the curious wording. Compared to a
thin concentrated sample, the effect might better be described as
saturation, while compared to a thick dilute sample, it's
actually related to a lack of absorption by other elements.
--Scott Calvin
Faculty at Sarah Lawrence College
Currently on sabbatical at Stanford Synchrotron Radiation Laboratory
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