[Ifeffit] P K-edge EXAFS

[Robert Gordon]

Hi,
You could try X-ray emission rather than EXAFS. It has shown some 
success in showing changes
in phosphate environment with bonding environment.

e.g. https://pubs.rsc.org/en/content/articlelanding/2021/sc/d1sc01266e

cheers,
-R.


On 2023-09-13 12:47 p.m., matthew marcus wrote:
> 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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