Re: [Ifeffit] Sulfur EXAFS k oscillations

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: ecmiller@slac.stanford.edumailto:ecmiller@slac.stanford.edu