[Ifeffit] S XANES question

[Matt Newville]

Hi Matthew, Lyle,

I'm still learning S XANES, but when we've measured gypsum, it looks very
comparable to the spectra from ID21:
   http://www.esrf.eu/UsersAndScience/Experiments/Imaging/ID21/php/gypsum

We often use the spectra from there as references (or when asking: Is this
"standard" what we think it is?)

--Matt



On Wed, Nov 26, 2014 at 4:23 PM, Matthew Marcus <mamarcus at lbl.gov> wrote:

> The gypsum spectrum looks nothing like any spectrum of gypsum or other
> sulfate I've ever seen.  I'm deeply suspicious.
>         mam
>
> On 11/26/2014 1:36 PM, Lyle Gordon wrote:
>
>> Matthew,
>>
>> Paris et al in 2001 reported higher S K-edge white line energies for SO4
>> in Apatite, 2 eV above Gypsum.
>>
>> THE VALENCE AND SPECIATION OF SULFUR IN GLASSES
>> BY X-RAY ABSORPTION SPECTROSCOPY
>> The Canadian Mineralogist
>> Vol. 39, pp. 331-339 (2001)
>>
>> -Lyle
>>
>> On Wed, Nov 26, 2014 at 12:39 PM, Matthew Marcus <mamarcus at lbl.gov
>> <mailto:mamarcus at lbl.gov>> wrote:
>>
>>     A user on ALS 10.3.2 is taking S K-edge XANES and consistently
>> finding a strong peak at 2484eV (calibration: gypsum white line =
>> 2482.75eV).
>>     There's a shoulder at the nominal position of the sulfate peak.  Now,
>> peaks below sulfate I can understand, but since there's no such
>>     thing as heptavalent sulfur, what could give a peak *above* the
>> sulfate white line?  Anybody ever seen that?  Yes, we checked calibration.
>>              mam
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-- 
--Matt Newville <newville at cars.uchicago.edu> 630-252-0431
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