[Ifeffit] P K-edge EXAFS

[Mike Massey]

The other difficulty I have experienced with P EXAFS is that a lot of the second-shell backscatterers are fairly weak, so picking that signal out is pretty difficult.

I have some spectra of minerals and that's where I've wanted to start with P EXAFS (since the structures are well-constrained). But as has been mentioned, low-frequency oscillations and background subtraction have massive impacts on the P K-edge EXAFS function (tested this by taking spectra of the same sample during different runs and getting different EXAFS due to slightly different background).

I don't think it's necessarily impossible, I just personally put it in the not-right-now basket.





> On Sep 14, 2023, at 07:42, Mike Massey <mmassey at gmail.com> 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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