[Ifeffit] Ifeffit Digest, Vol 88, Issue 4

Jatinkumar Rana jatinkumar.rana at helmholtz-berlin.de
Tue Jun 8 03:37:28 CDT 2010


Dear Dominik,

Thank you so very much for your detailed explanation about the effects 
of particle size on XAFS spectra.

Warm wishes,
Rana



On 07.06.2010 19:00, ifeffit-request at millenia.cars.aps.anl.gov wrote:
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> Today's Topics:
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>     1. particle size effects on XAFS spectra (Jatinkumar Rana)
>     2. Re: particle size effects on XAFS spectra (Dominik Samuelis)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 07 Jun 2010 14:49:33 +0200
> From: Jatinkumar Rana<jatinkumar.rana at helmholtz-berlin.de>
> To: Ifeffit users<ifeffit at millenia.cars.aps.anl.gov>
> Subject: [Ifeffit] particle size effects on XAFS spectra
> Message-ID:<4C0CEADD.8040600 at helmholtz-berlin.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Dear Users,
>
> I am working with the EXAFS technique for the characterization of my
> powder sample. I must admit that i am very much new to the technique and
> its analysis. I have read many tutorials on preparing sample for XAFS
> measurement (both transmission and fluoroscence). However, i am dealing
> with the powder having particle size much more smaller than one
> absorption length.
>
> I would like to know will it create any destructive effect on my XAFS
> spectra ??
>
> Many thanks in advance...
>
> Warm wishes,
> Rana
>
>
> ------------------------------
>
> Message: 2
> Date: Mon, 07 Jun 2010 15:21:14 +0200
> From: Dominik Samuelis<d.samuelis at fkf.mpg.de>
> To: XAFS Analysis using Ifeffit<ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] particle size effects on XAFS spectra
> Message-ID:<4C0CF24A.10407 at fkf.mpg.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Dear Rana,
>
> yes, it will have effects on your XAFS spectra, but not really
> destructive. EXAFS only really vanishes if you have isolated atoms. As
> long as your particles still have several hundred atoms with some
> coordination shell-like ordering, EXAFS oscillations will show up.
>
> However, the amplitude of the XAFS signals will be smaller than in bulk
> material, due to the lower average coordination number of the central
> atoms. If you e.g. have 5 nm particles (some 2000 atoms), already almost
> half of the atoms (~800) is sitting on the particle surface and
> therefore has a reduced coordination number.
>
> There's a wealth of information in literature where people actually use
> this effect for determining the particle size from XAFS.
>
> Another thing to keep in mind is that often it's not really clear how
> the surfaces of a particle looks like chemically - there might be
> adsorbates, or even passivation layers. If you're e.g. doing EXAFS on
> untreated 5nm Si particles, you can't really expect to see anything
> close to bulk Si, because the top layer might be SiO2
>
> Best regards,
> Dominik
>
>
>
> On 07.06.2010 14:49, Jatinkumar Rana wrote:
>    
>> Dear Users,
>>
>> I am working with the EXAFS technique for the characterization of my
>> powder sample. I must admit that i am very much new to the technique and
>> its analysis. I have read many tutorials on preparing sample for XAFS
>> measurement (both transmission and fluoroscence). However, i am dealing
>> with the powder having particle size much more smaller than one
>> absorption length.
>>
>> I would like to know will it create any destructive effect on my XAFS
>> spectra ??
>>
>> Many thanks in advance...
>>
>> Warm wishes,
>> Rana
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>      
>
>    




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