Re: [Ifeffit] Ca EXAFS with Ge220 or InSb111 (Lisa Bovenkamp)
Hello. No, the resolution is fine. I can do XANES fine with InSb111. We use those for years. Just had problems with EXAFS because for this long range the flux has to be more stable from the crystals. Lisa
I found Ca EXAFS files on my data directory which go out to 600eV above the edge, done using Si111. What's the symptom of the failure with InSb? Could harmonics be the problem? If there's something mechanical going on with the mono such that you go through the max of the rocking curve, then as you go through that max, you get more harmonics, which cause normalization failure. mam On 5/11/2015 11:06 AM, Lisa Bovenkamp wrote:
Hello.
No, the resolution is fine. I can do XANES fine with InSb111. We use those for years. Just had problems with EXAFS because for this long range the flux has to be more stable from the crystals.
Lisa _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Another possibility is that the L-edges of In and Sb are giving considerable energy-dependence to the beam in the EXAFS region...any non-linearity between detectors will make extraction of the EXAFS problematic. Looking at CAMD's XAS beamline mono specs http://www.camd.lsu.edu/beamline_info/DCM_beamline_2008.pdf Si111, Si220 and Ge220 will all cover the Ca K-edge range. -R. On 5/11/2015 3:46 PM, Matthew Marcus wrote:
I found Ca EXAFS files on my data directory which go out to 600eV above the edge, done using Si111. What's the symptom of the failure with InSb? Could harmonics be the problem? If there's something mechanical going on with the mono such that you go through the max of the rocking curve, then as you go through that max, you get more harmonics, which cause normalization failure. mam
On 5/11/2015 11:06 AM, Lisa Bovenkamp wrote:
Hello.
No, the resolution is fine. I can do XANES fine with InSb111. We use those for years. Just had problems with EXAFS because for this long range the flux has to be more stable from the crystals.
Lisa _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Hi Robert, Lisa,
On Mon, May 11, 2015 at 3:51 PM, Robert Gordon
Another possibility is that the L-edges of In and Sb are giving considerable energy-dependence to the beam in the EXAFS region...any non-linearity between detectors will make extraction of the EXAFS problematic. Looking at CAMD's XAS beamline mono specs http://www.camd.lsu.edu/beamline_info/DCM_beamline_2008.pdf Si111, Si220 and Ge220 will all cover the Ca K-edge range.
I completely agree. The In L edges (3730, 3938, 4238 eV) and Sb L edges (4132, 4380, 4698 eV) would make InSb pretty close to impossible to use as a mono for Ca K edge (4038 eV). --Matt
Hi Lisa, Just to second Matthew's suggestion, Si(111) should work fine for Ca K edge. In my experience, using high angle makes it much more challenging to keep a stable beam -- roll errors become more important, and thermal load can also be worse (power density on 1st crystal, heating from scattering on the second). So, in that sense, and if it's an option, Si(111) (at ~30 degrees) seems preferable to Ge(220) (at ~50 degrees, I believe). Hello. No, the resolution is fine. I can do XANES fine with InSb111. We use those for years. Just had problems with EXAFS because for this long range the flux has to be more stable from the crystals. Lisa _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
participants (4)
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Lisa Bovenkamp -
Matt Newville -
Matthew Marcus -
Robert Gordon