Re: [Ifeffit] Sulfur EXAFS k oscillations

[Miller, Elizabeth Christine]

Hi all,

Thanks for your suggestions! I will have a look at the spline parameters and 
try to replot as needed. 

Cheers,
Beth 

-Original Message-
From: Jeffrey Catalano  
Sent: Tuesday, April 10, 2018 10:53 AM
To: Miller, Elizabeth Christine 
Cc: ifeffit@millenia.cars.aps.anl.gov
Subject: Re: [Ifeffit] Sulfur EXAFS k oscillations

Actually, I have seen effects this like with the Spline Clamps turned up like 
you have them. What does this look like if you set Spline Clamps, both low and 
high, to none? Also, you should plot the full XAFS (in E, the whole thing, with 
the edge) and look at the background curve. My guess is it is oscillating and 
not doing a good job splining the data.

Jeff

On 4/10/2018 12:36 PM, Carlo Segre wrote:
>
> Hi Beth:
>
> I suggest that you not use kw=3 as that will make these background 
> subtraction oscillations worse.
>
> Another thing you can try is to cut down the high end of your spline 
> range to 13, then 12.5 and see if that makes it behave a bit better.
> I find that it helps a lot when the data is a bit noisy or there is a 
> slightly wavy background.  I also look at the FT to see how the 
> background spline is doing.
>
> Carlo
>
> On Mon, 9 Apr 2018, Miller, Elizabeth Christine wrote:
>
>> Hi all,
>>
>> I am analyzing some sulfur K-edge EXAFS data taken at 4-3 at SSRL. 
>> When I use a k-weight of k^3 to plot, my oscillations at high k reach 
>> over 100, which doesn't make sense to me. I have looked over the data 
>> with Riti, and it seems that while the XANES are rather self-absorbed 
>> due to high concentrations of sulfur-containing salt, the data can be 
>> normalized, and the EXAFS should contain some information. I've 
>> included screenshots in the attachment of plots of all of the 
>> k-weights as well as my parameters. The mixtures are solutions of 
>> organics (acetonitrile, 1,1,2,2-Tetrafluoroethyl 
>> 2,2,3,3-tetrafluoropropyl ether) with 
>> bis(trifluoromethane)sulfonimide lithium salt. I am also not hitting 
>> any other edges, as sulfur is the highest Z element in the solution.
>> Any thoughts would be greatly appreciated!
>>
>> Thank you,
>> Beth
>>
>>
>>
>> Elizabeth C. Miller, Ph.D.
>> Postdoctoral Scholar
>> Stanford Synchrotron Radiation Lightsource SLAC National Accelerator 
>> Laboratory
>>
>> E-mail: ecmil...@slac.stanford.edu<mailto:ecmil...@slac.stanford.edu>
>>
>>
>


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Re: [Ifeffit] Sulfur EXAFS k oscillations

[Jeffrey Catalano]

Actually, I have seen effects this like with the Spline Clamps turned up 
like you have them. What does this look like if you set Spline Clamps, 
both low and high, to none? Also, you should plot the full XAFS (in E, 
the whole thing, with the edge) and look at the background curve. My 
guess is it is oscillating and not doing a good job splining the data.


Jeff

On 4/10/2018 12:36 PM, Carlo Segre wrote:


Hi Beth:

I suggest that you not use kw=3 as that will make these background 
subtraction oscillations worse.


Another thing you can try is to cut down the high end of your spline 
range to 13, then 12.5 and see if that makes it behave a bit better.  
I find that it helps a lot when the data is a bit noisy or there is a 
slightly wavy background.  I also look at the FT to see how the 
background spline is doing.


Carlo

On Mon, 9 Apr 2018, Miller, Elizabeth Christine wrote:


Hi all,

I am analyzing some sulfur K-edge EXAFS data taken at 4-3 at SSRL. 
When I use a k-weight of k^3 to plot, my oscillations at high k reach 
over 100, which doesn't make sense to me. I have looked over the data 
with Riti, and it seems that while the XANES are rather self-absorbed 
due to high concentrations of sulfur-containing salt, the data can be 
normalized, and the EXAFS should contain some information. I've 
included screenshots in the attachment of plots of all of the 
k-weights as well as my parameters. The mixtures are solutions of 
organics (acetonitrile, 1,1,2,2-Tetrafluoroethyl 
2,2,3,3-tetrafluoropropyl ether) with 
bis(trifluoromethane)sulfonimide lithium salt. I am also not hitting 
any other edges, as sulfur is the highest Z element in the solution. 
Any thoughts would be greatly appreciated!


Thank you,
Beth



Elizabeth C. Miller, Ph.D.
Postdoctoral Scholar
Stanford Synchrotron Radiation Lightsource
SLAC National Accelerator Laboratory

E-mail: ecmil...@slac.stanford.edu






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Re: [Ifeffit] Sulfur EXAFS k oscillations

[Carlo Segre]

Hi Beth:

I suggest that you not use kw=3 as that will make these background 
subtraction oscillations worse.


Another thing you can try is to cut down the high end of your spline range 
to 13, then 12.5 and see if that makes it behave a bit better.  I find 
that it helps a lot when the data is a bit noisy or there is a slightly 
wavy background.  I also look at the FT to see how the background spline 
is doing.


Carlo

On Mon, 9 Apr 2018, Miller, Elizabeth Christine wrote:


Hi all,

I am analyzing some sulfur K-edge EXAFS data taken at 4-3 at SSRL. When I use a 
k-weight of k^3 to plot, my oscillations at high k reach over 100, which 
doesn't make sense to me. I have looked over the data with Riti, and it seems 
that while the XANES are rather self-absorbed due to high concentrations of 
sulfur-containing salt, the data can be normalized, and the EXAFS should 
contain some information. I've included screenshots in the attachment of plots 
of all of the k-weights as well as my parameters. The mixtures are solutions of 
organics (acetonitrile, 1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl 
ether) with bis(trifluoromethane)sulfonimide lithium salt. I am also not 
hitting any other edges, as sulfur is the highest Z element in the solution. 
Any thoughts would be greatly appreciated!

Thank you,
Beth



Elizabeth C. Miller, Ph.D.
Postdoctoral Scholar
Stanford Synchrotron Radiation Lightsource
SLAC National Accelerator Laboratory

E-mail: ecmil...@slac.stanford.edu




--
Carlo U. Segre -- Duchossois Leadership Professor of Physics
Interim Chair, Department of Chemistry
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498Fax: 312.567.3494
se...@iit.edu   http://phys.iit.edu/~segre   se...@debian.org
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Re: [Ifeffit] Sulfur EXAFS k oscillations

[Robert Gordon]

Large mono glitch around k ~ 13.8 A-1  (E~3200 eV) on 4-3   perhaps?

On 4/9/2018 11:04 AM, Miller, Elizabeth Christine wrote:


Hi all,

I am analyzing some sulfur K-edge EXAFS data taken at 4-3 at SSRL. 
When I use a k-weight of k^3 to plot, my oscillations at high k reach 
over 100, which doesn’t make sense to me. I have looked over the data 
with Riti, and it seems that while the XANES are rather self-absorbed 
due to high concentrations of sulfur-containing salt, the data can be 
normalized, and the EXAFS should contain some information. I’ve 
included screenshots in the attachment of plots of all of the 
k-weights as well as my parameters. The mixtures are solutions of 
organics (acetonitrile, 1,1,2,2-Tetrafluoroethyl 
2,2,3,3-tetrafluoropropyl ether) with bis(trifluoromethane)sulfonimide 
lithium salt. I am also not hitting any other edges, as sulfur is the 
highest Z element in the solution. Any thoughts would be greatly 
appreciated!


Thank you,

Beth

Elizabeth C. Miller, Ph.D.

Postdoctoral Scholar

Stanford Synchrotron Radiation Lightsource

SLAC National Accelerator Laboratory

E-mail: ecmil...@slac.stanford.edu 



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