[Ifeffit] P K-edge EXAFS

[matthew marcus]

Good points.  At these low energies, an EXAFS range is a large fraction 
of the total energy range, so there tends to be a lot of curvature of 
baselines and post-edges.  True about the 4O 1NN shell that dominates, 
but the same happens with As.  All the interesting stuff is in the 
higher shells.  Most data I've seen has been XANES.
	mam

On 9/13/2023 12:42 PM, Mike Massey wrote:
> In my experience the main difficulties with EXAFS on P (phosphate) come 
> from two factors (not signal to noise, it's not hard to get a nice 
> smooth line, but):
> 
> 1) You've got 4 O atoms, guaranteed, so any other signal will be small 
> and on top of that very strong signal generated from the first-neighbor O
> 
> Unfortunately,
> 
> 2) You have very limited data range, either due to instrumental 
> limitations, or due to interference from sulfur
> 
> Don't get me wrong I still have some data sitting around and I'd love to 
> try P EXAFS analysis on it just to try and grasp that brass ring 
> but...It's not the easiest task ever.
> 
> If you want good data quality "scan longer" is always an option. Some 
> might think it's crazy but I do think I have some P XAS data where I 
> took 30 or 60 scans, maybe overnight or something. The scans are so 
> short that repeats are easy.
> 
> 
> Hope this commentary is helpful.
> 
> 
> 
> Mike
> 
> 
> 
> 
>> On Sep 14, 2023, at 07:04, Marcelo Eduardo Alves <mealves at gmail.com> 
>> wrote:
>>
>> 
>>
>> Hi there,
>>
>> I begin by examining phosphorus adsorption by goethite, hematite, and 
>> gibbsite.
>>
>> Why is it difficult, if not impossible, to obtain EXAFS spectra at the 
>> P-K edge that can be properly used, i.e., spectra with a high 
>> signal-to-noise ratio, especially for dilute samples?
>>
>> Would it be possible to use arsenic as a phosphorus proxy to get 
>> conclusions from As K-edge EXAFS data that could be extended to P?
>>
>> Thank you.
>>
>>
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