Re: [Ifeffit] Ifeffit Digest, Vol 172, Issue 15

2017-06-22 Thread Weizi Yuan
Hi Anatoly,
Thanks for your quick response.
Yes, I actually asked the self absorption question about CeO2 a few weeks
ago. And your answer that it is due to self absorption leads me to study
more about it and I appreciate it.
In that last question, the strong attenuation of signal occurs in the
incident angle = 0.6 o . However, when the incident angle is 3 o  under
room temperature ,air, the peak intensity is stronger than the CeO2
measured in  transmission mode, which leads me to think that no over
absorption correction needed here. And I try to  conduct the correction
which gives me crazily high (~9 after normalization) peak intensity.
This makes me further confirm that no strong self absorption effect here.
And if no strong self absorption in RT, air ,then why strong attenuation in
RT, vacuum condition(case ii in my question)?
For your answer,I am a little confused. Are you saying self absorption
occurred in only case ii or in both cases, even though the result of case i
spectrum has a higher signal than the transmission mode data?
Thank you,
Weizi


On Thu, Jun 22, 2017 at 10:16 AM, <ifeffit-requ...@millenia.cars.aps.anl.gov
> wrote:

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>1. Self absorption or Ce4+ reduction in the CeO2 film? (Weizi Yuan)
>
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> Message: 1
> Date: Thu, 22 Jun 2017 10:11:05 -0500
> From: Weizi Yuan <weiziyuan2...@u.northwestern.edu>
> To: ifeffit@millenia.cars.aps.anl.gov
> Subject: [Ifeffit] Self absorption or Ce4+ reduction in the CeO2 film?
> Message-ID:
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> Content-Type: text/plain; charset="utf-8"
>
> Dear all,
> I have measured some spectra of a CeO2 film(~200nm) grown on Yittria
> stablized Zirconia(YSZ) substrate under 2 conditions.
> (i) room temperature, ambient atmosphere
> (ii) room temperature, vacuum (pO2~1E-6 atm) inside a graphite dome of  the
> DHS 1100 anton paar,
> The spectra are collected in fluorescence mode. The incident angle is 3 o
>  and the fluorescence collection angle is 90 o.
>
> My questions are:
> (i) From the theory behind the FLUO program developed Dr. Daniel Haskel,
> CeO2 spectra collected with a 3 o incident angle *would have a strong self
> absorption effect and need*
>
>  correction , however, *the signal *is not attenuated compared with the
> CeO2 powder taken in a transmission mode, shown in attached plot.
> I've gone through many literature and people sometimes tell that whether
>  they have a successful self absorption correction by comparing the
> spectrum with a spectrum taken under a transmission mode.
> So I'm wondering if I can say that I don't need a self absorption
> correction in this case?
> (ii)
> The Ce4+ peak in the spectrum collected under condition (ii) has a much
> lower intensity. I think it is due to the reduction of Ce 4+ under vacuum,
> however, the Ce3+ peak does not show an increased signal here. Which makes
> ma doubt whether this is simply reduction of Ce *or might be from over
> absorption? *
>
> Thanks for any response.
>
> [image: Inline image 1]
> --
> Regards,
> Weizi Yuan,
> Graduate Student,
> Northwestern University,
> Ph:(+1)312-560-9619
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> End of Ifeffit Digest, Vol 172, Issue 15
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>



-- 
Regards,
Weizi Yuan,
Graduate Student,
Northwestern University,
Ph:(+1)312-560-9619
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Re: [Ifeffit] Self absorption in CeO2 spectrum

2017-05-23 Thread Weizi Yuan
Thank you for your kind suggestion, Fred. It gives me some ideas of how to
design my next experiment. And I will also try to do self absorption
correction and see if it helps at the current stage.
Weizi

-- 
Regards,
Weizi Yuan,
Graduate Student,
Northwestern University,
Ph:(+1)312-560-9619
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Re: [Ifeffit] Ifeffit Digest, Vol 171, Issue 14

2017-05-19 Thread Weizi Yuan
Got it.
Thanks for the response, Anatoly.
Weizi


On Fri, May 19, 2017 at 4:37 PM, <ifeffit-requ...@millenia.cars.aps.anl.gov>
wrote:

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> Today's Topics:
>
>1. Self absorption in CeO2 spectrum (Weizi Yuan)
>
>
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> Message: 1
> Date: Fri, 19 May 2017 16:37:54 -0500
> From: Weizi Yuan <weiziyuan2...@u.northwestern.edu>
> To: ifeffit@millenia.cars.aps.anl.gov
> Subject: [Ifeffit] Self absorption in CeO2 spectrum
> Message-ID:
> 

[Ifeffit] Self absorption in CeO2 spectrum

2017-05-19 Thread Weizi Yuan
Dear all,
I have measured some XANES spectra of CeO2 film(~220nm) in fluorescence
mode at Ce L3 edge with two incident angles of 0.6 degree and 3 degree. My
goal is to get relative surface sensitive (penetration depth~ 20 nm above
edge) information of [Ce3+] from 0.6 o  while bulk sensitive information at
3 o (penetration depth~ 160 nm above edge). In the meantime, I also
collected CeO2 powder reference spectrum under transmission mode. The
comparison is shown in the graph.
The film at 3 degree has a sharper white line than the powder while at 0.6
degree, it is the opposite. I think this might be because at the surface of
the film,it has more Ce3+ while when we detect the bulk it has more Ce4+.
My question  is how can I tell if I need self-absorption correction or not
for the films in this case? Can I say I do not need self absorption
correction because I have a higher normalized u for the film collected in
the fluorescence mode than powder collected in the transmission mode?
Thanks a lot for your comments.
Weizi
[image: Inline image 1]


-- 
Regards,
Weizi Yuan,
Graduate Student,
Northwestern University,
Ph:(+1)312-560-9619
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