On Mon, Oct 10, 2011 at 11:42 AM,
<ifeffit-request@millenia.cars.aps.anl.gov> wrote:
Send Ifeffit mailing list submissions to
ifeffit@millenia.cars.aps.anl.gov
To subscribe or unsubscribe via the World Wide Web, visit
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
or, via email, send a message with subject or body 'help' to
ifeffit-request@millenia.cars.aps.anl.gov
You can reach the person managing the list at
ifeffit-owner@millenia.cars.aps.anl.gov
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Ifeffit digest..."
Today's Topics:
1. Re: number of independent points (George Sterbinsky)
2. Re: lifetime broadening of pre-edge peaks? (Matthew Marcus)
3. Re: lifetime broadening of pre-edge peaks? (Anatoly I Frenkel)
----------------------------------------------------------------------
Message: 1
Date: Mon, 10 Oct 2011 14:04:07 -0400
From: George Sterbinsky <GeorgeSterbinsky@u.northwestern.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] number of independent points
Message-ID:
<CALoY8YwBz3jLWTLX+dosjiXs6Fv3RpG_UfG2yEz-X3XVn17abg@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Bruce, Matt, and Jeremy,
Thank you for explaining this. Your responses are much appreciated.
George
On Mon, Oct 10, 2011 at 11:35 AM, Bruce Ravel <bravel@bnl.gov> wrote:
> On Monday, October 10, 2011 10:35:12 am George Sterbinsky wrote:
> > Since I haven't received a response to my previous question, I just
> wanted
> > to make sure I asked it clearly.
>
> I suspect the lack of response had more to do with it being a
> non-trivial question asked on a Friday afternoon :)
>
> > To elaborate, I am attaching a log from
> > Athena. The log file lists:
> >
> > "Independent points = 27.057617188"
> >
> > If I attempt to reproduce this result using the equation in the feffit
> > document, I find
> >
> > Nidp = { [2*(kmax - kmin)*(Rmax-Rmin) / pi] + 2} = { [2*(14 - 0.5)*(4.2 -
> > 1.0) / pi] + 2} = 29.50197417,
> >
> > where I have used the k-range and R-range in the log file as kmax, kmin,
> > Rmax, and Rmin.
> >
> > Can someone explain to me why may calculation does not reproduce the
> number
> > given for "independent points" in the log fie?
>
> George,
>
> A quick examination of the ifeffit source code shows that there are
> two issues:
>
> 1. Regardless of what it may say in the document, Ifeffit uses "+0"
> rather than "+2". See line 345 of
> http://cars9.uchicago.edu/svn/ifeffit/trunk/src/lib/iff_feffit.f
>
> A bit of history: Ed Stern wrote this paper back in 1993:
> http://dx.doi.org/10.1103/PhysRevB.48.9825
>
> Over the years, many have expressed scepticism of his conclusion.
> The Bayesian work I mentioned earlier suggests quibbling over the
> value of N in the "+N" term misses the bigger issue. Ifeffit's
> use of "+0" provides a conservative yet easily stated estimate of
> Nidp.
>
> 2. The difference to the left of the decimal point has to do with the
> fact that Artemis allows you to pick any value for kmin, kmax,
> rmin, and rmax. When Ifeffit evaluates Nidp (and anything else)
> is actually takes the nearest grid points to those four values.
> The grid in k-space is 0.05 inv. Angstroms. This sets the grid in
> R space to be about 0.03 Angstroms, but not exactly. So the
> values of Rmax and Rmin used by Ifeffit to compute Nidp (and other
> things) are not quite what you specified.
>
> At some point, George, you may want to bite the bullet and look at
> source code. Details are not unknowable, they just might not be
> written down anywhere beside the source code.
>
> Here is the top of Ifeffit:
> http://cars9.uchicago.edu/svn/ifeffit/trunk/
>
> B
>
>
> --
>
> Bruce Ravel ------------------------------------ bravel@bnl.gov
>
> National Institute of Standards and Technology
> Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
> Building 535A
> Upton NY, 11973
>
> My homepage: http://xafs.org/BruceRavel
> EXAFS software: http://cars9.uchicago.edu/ifeffit/Demeter
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111010/2888a524/attachment-0001.htm>
------------------------------
Message: 2
Date: Mon, 10 Oct 2011 11:23:07 -0700
From: "Matthew Marcus" <mamarcus@lbl.gov>
To: "XAFS Analysis using Ifeffit" <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] lifetime broadening of pre-edge peaks?
Message-ID: <6BBC1B5DFDEE4BE1902489451655B16B@als.lbl.gov>
Content-Type: text/plain; charset="iso-8859-2"
Thanks. While none of these have to do with pre-edge peaks such as are found in transition-metal oxides, the assumption of constancy of core-hole broadening does seem to work.
mam
----- Original Message -----
From: Iztok Ar?on
To: XAFS Analysis using Ifeffit
Sent: Monday, October 10, 2011 12:32 AM
Subject: Re: [Ifeffit] lifetime broadening of pre-edge peaks?
Dear Matthew
you can find examples of determination of life-time broadening, deconvolution of XANES specra, and discussion about limitations due to noise in several papers, for example:
A. Filipponi, J. Phys. B 33, 2835 (2000)
A. Kodre, I. Ar?on, J. Padeznik Gomil?ek, R. Frahm
J. Phys. B: At. Mol. Opt. Phys. 35 (2002) 3497-3513
A. Kodre, J. Pade?nik Gomil?ek, A. Miheli?, I. Arcon
Radiation Physics and Chemistry 75 (2006) 188-194
J. Padeznik Gomilsek, I. Arcon, S. de Panfilis, A. Kodre,
Phys. Rev. A 79, (2009) 032514,
regards
Iztok
Matthew Marcus wrote:
Is the core-hole lifetime broadening of pre-edge XANES peaks the same as at the main edge? I'm looking into issues of de-noising of XANES epsctra, so
need to figure out how narrow real features can be.
mam
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
--
prof. dr. Iztok Arcon
University of Nova Gorica
Vipavska 13, POB 301
5001 Nova Gorica, Slovenia
tel: +386 5 331 5227
fax: +386 5 331 5240
e-mail: iztok.arcon@ung.si
http://www.ung.si/~arcon
http://www.ung.si/~arcon/xas
------------------------------------------------------------------------------
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111010/95c745d3/attachment-0001.htm>
------------------------------
Message: 3
Date: Mon, 10 Oct 2011 18:42:07 +0000
From: Anatoly I Frenkel <afrenke2@yu.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] lifetime broadening of pre-edge peaks?
Message-ID:
<545F89325F51764C902D37B42C9F4D539B55E9@YUWEXCPM11.yuad.uds.yu.edu>
Content-Type: text/plain; charset="iso-8859-2"
I think experimental answer could be the simplest one. Perhaps there is anyone on the list who measured low concentrations of low Z absorber in the high Z host at both edges?
For example, Cu in Ag (if does dissolve in Ag if made by rapid quenching) at Cu K-edge, and Ag K-edge (or just bulk Ag since the data will be the same). These should be solid solutions, of course.
Then, despite the difference in phase shift, the EXAFS oscillations should be comparable in magnitude if the broadening is not significant, and it should be more intense for the Cu K-edge if the broadening at Ag K edge is significant.
Another option: to hear from people doing HERFD. That is normally done on XANES, for the reason, I assume, that they do not see any advantage in EXAFS region, where broadening does not change compared to total fluorescence.
I think the explanation that EXAFS should not be too sensitive to the life time broadening is that EXAFS originates from the final state interference, while the XANES - from both the final state interference and DOS. But may be experiments are showing the opposite, and that will prove me wrong.
Anatoly
________________________________
From: ifeffit-bounces@millenia.cars.aps.anl.gov [ifeffit-bounces@millenia.cars.aps.anl.gov] on behalf of Matthew Marcus [mamarcus@lbl.gov]
Sent: Monday, October 10, 2011 2:23 PM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] lifetime broadening of pre-edge peaks?
Thanks. While none of these have to do with pre-edge peaks such as are found in transition-metal oxides, the assumption of constancy of core-hole broadening does seem to work.
mam
----- Original Message -----
From: Iztok Ar?on<mailto:iztok.arcon@ung.si>
To: XAFS Analysis using Ifeffit<mailto:ifeffit@millenia.cars.aps.anl.gov>
Sent: Monday, October 10, 2011 12:32 AM
Subject: Re: [Ifeffit] lifetime broadening of pre-edge peaks?
Dear Matthew
you can find examples of determination of life-time broadening, deconvolution of XANES specra, and discussion about limitations due to noise in several papers, for example:
A. Filipponi, J. Phys. B 33, 2835 (2000)
A. Kodre, I. Ar?on, J. Padeznik Gomil?ek, R. Frahm
J. Phys. B: At. Mol. Opt. Phys. 35 (2002) 3497-3513
A. Kodre, J. Pade?nik Gomil?ek, A. Miheli?, I. Arcon
Radiation Physics and Chemistry 75 (2006) 188-194
J. Padeznik Gomilsek, I. Arcon, S. de Panfilis, A. Kodre,
Phys. Rev. A 79, (2009) 032514,
regards
Iztok
Matthew Marcus wrote:
Is the core-hole lifetime broadening of pre-edge XANES peaks the same as at the main edge? I'm looking into issues of de-noising of XANES epsctra, so
need to figure out how narrow real features can be.
mam
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov<mailto:Ifeffit@millenia.cars.aps.anl.gov>
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
--
prof. dr. Iztok Arcon
University of Nova Gorica
Vipavska 13, POB 301
5001 Nova Gorica, Slovenia
tel: +386 5 331 5227
fax: +386 5 331 5240
e-mail: iztok.arcon@ung.si<mailto:iztok.arcon@ung.si>
http://www.ung.si/~arcon
http://www.ung.si/~arcon/xas
________________________________
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111010/d38ac810/attachment.htm>
------------------------------
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
End of Ifeffit Digest, Vol 104, Issue 13
****************************************