[Ifeffit] Origin of terminology "self-absorption"

[Ponader, Carl W Dr]

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-bounces at millenia.cars.aps.anl.gov
[mailto:ifeffit-bounces at 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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