[Ifeffit] Origin of terminology "self-absorption"

Matt Newville newville at cars.uchicago.edu
Tue Nov 16 13:23:39 CST 2010


It's a term taken from x-ray fluorescence spectroscopy, or probably
really any fluorescence spectroscopy, where it has very sensible
meaning: the attenuation of the fluorescence signal by the sample
itself.  I would even say it is used "mostly correctly" in XAFS, or at
least with a similar intent as the original term, much as the term
Debye-Waller Factor is used.

--Matt

On Tue, Nov 16, 2010 at 1:01 PM, Scott Calvin <dr.scott.calvin at gmail.com> wrote:
> 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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