Bruce Ravel | 2 Feb 21:30 2016
Gravatar

Re: Could you please give me some information?

On 02/01/2016 11:58 PM, pinit wrote:
> Dear Bruce,
>
> I am Pinit from SLRI, Thailand. I have some questions concerning the
> Si-drift detector.
>
> Could you give me some suggestions if Si-detector can detect the
> corrected Si K-edge or not? This is because I have seen a significant
> EXAFS signal (higher in amplitude in FT) measured by Si-drift detector
> differs from Lytle detector or ionization chambers (TM mode).

Hi Pinit,

Nice to hear from you.  I am CCing my answer to the Ifeffit Mailing
List.  Someone else may have more insight into your question than I
do.  You should CC the list in your response.

I'd probably need to know more about the sample and the nature of the
measurement you made to understand why you are seeing a different
signal with the Si drift detector.

Normally one would expect that he EXAFS would be /attenuated/ either
due to self-absorption or due to the energy dependence of the I0
detector.  That you are seeing a larger EXAFS signal with the Si-drift
seems surprising.

One thing that occurs to me is that the Compton and elastic peaks
probably overlap the Si K alpha ROI quite a bit, even extending into
the EXAFS region.  I would have thought that, too, would serve to
attenuate the EXAFS (but maybe I am thinking about that wrongly).
(Continue reading)

Manuel Cossio Kohler | 1 Feb 23:16 2016
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Athena with IOS "El Capitan"

Hello,

I am having some issues with the Athena software. After upgrading the OS of the macbook pro to "El Capitan" Version 10.11.3, Athena stopped working properly. Once the iXAFS icon was clicked nothing happened. I decided to do a bit of research and installed the latest verion of XQuartz version 2.7.8. I was able to launch athena by executting "athena" from the terminal. Up to that point, I figured that everything was running smoothly until I realized that I could prompt any plots. Something in the software or operating system was not allowing Athena to display plots. I would be really grateful if you could provide me with a solution to this problem (if there is any) or any advice that would allow me to process XAS data again. Thank you

Regards,

Manuel Cossio
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Avakyan L.A. | 1 Feb 00:39 2016
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Re: pi/2deltak

Hello Riti,

the criterion of R-resolution of pi/2deltak can be drawn from the 
Nyquist theorem.
The amount of information in the spectra is limited by Nidp = 2 deltak 
deltaR / pi.
Then, in assumption of equal distribution of information over the 
R-interval, the minimal interval can be estimated as deltaR / Nidp = 
pi/2deltak.
The problem is that exact formula for Nidp is not known. Sometimes it 
has addition of +1 or +2 to represent the fact that single point 
(deltak=0) still contains information.
Moreover, information is not equally distributed: some k-regions are 
more rich, other are less...

And when energy interval is very short (glass, liquid) this question 
becomes vital. Sometimes, this resolution limit can even be overcome as 
it is shown in [http://dx.doi.org/10.1103/PhysRevB.82.064204].

Best regards,
Leon

Leon Avakyan
PhDr, Physics Faculty,
Southern Federal University
laavakyan@...

On 31.01.2016 21:00,
ifeffit-request@... wrote:
> Message: 2
> Date: Sat, 30 Jan 2016 17:35:04 -0800
> From: Ritimukta Sarangi<ritimukta@...>
> To: XAFS Analysis using Ifeffit<ifeffit@...>
> Subject: [Ifeffit] pi/2deltak
> Message-ID:
> 	<CAMWiF7ymrKEDSZw31pcgwCzZH5tsFvFk+151gxfjRz9jUARH4w@...>
> Content-Type: text/plain; charset="utf-8"
>
> Hello,
>
> I was recently asked about the accuracy of this formulation for obtaining
> EXAFS resolution and I did not have a good answer. Can someone point to a
> reference or explain here?
> Thank you for your time,
> Best,
> -Riti

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Ritimukta Sarangi | 31 Jan 02:35 2016
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pi/2deltak

Hello,

I was recently asked about the accuracy of this formulation for obtaining EXAFS resolution and I did not have a good answer. Can someone point to a reference or explain here?
Thank you for your time,
Best,
-Riti

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Christopher Thomas Chantler | 30 Jan 21:31 2016
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Re: Ifeffit Digest, Vol 155, Issue 16

Dear Jason
Good topic

We have published a few papers discussing analysis with thickness distributions and roughness. Normally
the XERT method will address this especially for small samples.

Particularly see J. L. Glover, C. T. Chantler, M. D. de Jonge, ‘Nano-roughness in gold revealed from
X-ray signature,’ Physics Letters A373 (2009) 1177-1180. The general topic of thickness effects is of
course wider, and partially addressed in a couple of other papers.

Hope this helps
Chris
------------------------------------------------------------
Christopher Chantler, Professor, FAIP
Editor-in-Chief, Radiation Physics and Chemistry
Chair, International IUCr Commission on XAFS
President, International Radiation Physics Society
School of Physics, University of Melbourne
Parkville Victoria 3010 Australia
+61-3-83445437 FAX +61-3-93474783
chantler@... chantler@...
http://optics.ph.unimelb.edu.au/~chantler/xrayopt/xrayopt.html
http://optics.ph.unimelb.edu.au/~chantler/home.html

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Today's Topics:

   1. Re: Effect of gradual thickness variation in beam (Jason Gaudet)

----------------------------------------------------------------------

Message: 1
Date: Fri, 29 Jan 2016 14:32:43 -0500
From: Jason Gaudet <jason.r.gaudet@...>
To: XAFS Analysis using Ifeffit <ifeffit@...>
Subject: Re: [Ifeffit] Effect of gradual thickness variation in beam
Message-ID:
        <CANMcWtOLubiomegk-GM6SMS6CSpw0B0Hg21rMe9-hV8uQEkxhw@...>
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Hi Anatoly,

Sorry, I meant to write 1000 um inner diameter.

Energies will be V and Fe, 5465 & 7112 eV.  Samples are roughly 1
absorption length thick for the metal (V, Fe) and about 2-2.5 absorption
lengths for the entire sample.

Bruce,

I may just flip over the sample holder and have the sample tubes in plane
with the storage ring to take advantage of the greater horizontal spread,
rather than focusing on the vertical.  Cutting the vertical slits down to
100-300 um while keeping the horizontal around 500 um ought to get me the
most beam at the least variation in mu(E), especially if I go with 1500 um
ID tubes.  The samples are nice and concentrated so I can afford to give up
a lot of photon flux.  Bar-napkin calculations tell me with a 1500 um ID
tube and 200 um V 750 um H slits I'll lose an acceptable amount of photon
flux and have a <1% thickness variation.  I'm fairly confident I've made
pressed pellets with as much or more variation from one spot to another,
without noticeable mu(E) changes from spot to spot, in the vicinity of this
energy range.

I'll go ahead and take your advice, and amend my setup procedure with some
measurements of Io intensity and mu(E) reproducibility as a function of
slit width.  While a bit of a bother, it's still worth it to keep our
sample prep simple and inexpensive.

Thanks,

Jason

On Thu, Jan 28, 2016 at 9:12 AM, Bruce Ravel <bravel@...> wrote:

> On 01/27/2016 07:05 PM, Jason Gaudet wrote:
>
>> I'm planning on some transmission-mode XAS with smaller than usual
>> sample tubes.  I'm realizing I might be in danger of creating excessive
>> non-uniformity in my samples by having the beam size on the same order
>> of magnitude as the sample tube radius.
>>
>> For example, let's say I want to measure liquid in a sample tube with a
>> 1000 micron outer diameter, with a beam 500 microns wide and centered on
>> the sample tube. If the tube is orthogonal to the ring plane, the entire
>> vertical portion of the beam will pass through the same length of
>> liquid.  But in the horizontal plane, the center of the beam will pass
>> through 1000 microns of sample while the edges of the beam will pass
>> through 866 microns of sample, due to the curvature of the sample cell
>> across the horizontal plane.
>>
>> Most of what I know about the statistics of thickness effects are about
>> leakage and pinholes - nonlinearity caused by a few spots having very
>> low or negligible sample thickness.  But I don't know how significant a
>> "mild" thickness distribution might be.  If this sort of thickness
>> distribution is going to be an issue it would be great to know that
>> beforehand and either go with larger samples, smaller beam size, or more
>> creative orientation.
>>
>
>
> Jason,
>
> There may be some distortion to the data due to the varying thickness.
> On the plus side, liquids tend to be very homogeneous.
>
> Probably the best solution to this situation, if it's available at the
> beamline, is to focus the beam in the vertical, for example, using a
> flat mirror on a bender.  Focusing to a spot would also address the
> thickness situation, but you need to be mindful that the intense beam
> could generate radicals from the liquid, causing sample damage.
>
> If the sample is sufficiently concentrated, then you could simply slit
> the beam down to 100 or 200 microns and still have enough for a
> transmission measurement.  In fact, that would be the way to decide if
> you are seeing a big problem from the shape of the tube.  Compare the
> mu(E) with the slits at 500 to mu(E) with the slits at 100 (carefully
> aligning the sample both times, of course).  If they are the same,
> then, then you're golden.
>
> B
>
>
> --
>  Bruce Ravel  ------------------------------------ bravel@...
>
>  National Institute of Standards and Technology
>  Synchrotron Science Group at NSLS-II
>  Building 535A
>  Upton NY, 11973
>
>  Homepage:    http://bruceravel.github.io/home/
>  Software:    https://github.com/bruceravel
>  Demeter:     http://bruceravel.github.io/demeter/
> _______________________________________________
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Jason Gaudet | 28 Jan 01:05 2016
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Effect of gradual thickness variation in beam

Sample cell

Hi all,

I'm planning on some transmission-mode XAS with smaller than usual sample tubes.  I'm realizing I might be in danger of creating excessive non-uniformity in my samples by having the beam size on the same order of magnitude as the sample tube radius.

For example, let's say I want to measure liquid in a sample tube with a 1000 micron outer diameter, with a beam 500 microns wide and centered on the sample tube.  If the tube is orthogonal to the ring plane, the entire vertical portion of the beam will pass through the same length of liquid.  But in the horizontal plane, the center of the beam will pass through 1000 microns of sample while the edges of the beam will pass through 866 microns of sample, due to the curvature of the sample cell across the horizontal plane.

Most of what I know about the statistics of thickness effects are about leakage and pinholes - nonlinearity caused by a few spots having very low or negligible sample thickness.  But I don't know how significant a "mild" thickness distribution might be.  If this sort of thickness distribution is going to be an issue it would be great to know that beforehand and either go with larger samples, smaller beam size, or more creative orientation.

Thanks,

Jason


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Godfrey, Ian | 27 Jan 12:33 2016
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FW: Data summation - missing groups

Sorry, I’ve just seen that this has already been reported.

 

Ian

 

From: Godfrey, Ian
Sent: 27 January 2016 11:21
To: 'XAFS Analysis using Ifeffit' <ifeffit-yJARRRr6MatTopXEvdbuMjsBOjWwlrnm@public.gmane.orggov>
Subject: Data summation - missing groups

 

Dear All,

 

When using the data summation tool in Athena (0.9.24 x64 on Win10 Pro) the first group in the group list seems to be missing from the dropdown showing the potential components of a summation (see attached screenshot).

 

To reproduce:

 

1) Open attached project file and import with “select all” on the import dialogue box

2) Change to data summation window

3) Try and add the first data group (234) to the summation from the dropdown menus. (In the screenshot I’ve changed the default normmu(E) to mu(E), but the same behaviour is displayed in both cases.)

 

On a related note, I’m not sure I fully understand how the data summation is different from the merge? Clearly data summation allows you more control (arbitrary weighting of groups etc.) and is intended for XANES analysis, but is it a fundamentally different procedure or just a different interface for the same thing?

 

Thanks,

 

Ian

 

 

Ian Godfrey

 

PhD Student,

UCL/JAIST Programme

 

Industrial Doctorate Centre in Molecular Modelling and Materials Science,

Department of Chemistry,

University College London,

 

And

 

School of Materials Science,

Japan Advaned Institute of Science and Technology

 

i.godfrey <at> ucl.ac.uk i.godfrey-8xqbrEIV++l3+QwDJ9on6Q@public.gmane.org

 

02076 794864

 

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Godfrey, Ian | 27 Jan 12:21 2016
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Data summation - missing groups

Dear All,

 

When using the data summation tool in Athena (0.9.24 x64 on Win10 Pro) the first group in the group list seems to be missing from the dropdown showing the potential components of a summation (see attached screenshot).

 

To reproduce:

 

1) Open attached project file and import with “select all” on the import dialogue box

2) Change to data summation window

3) Try and add the first data group (234) to the summation from the dropdown menus. (In the screenshot I’ve changed the default normmu(E) to mu(E), but the same behaviour is displayed in both cases.)

 

On a related note, I’m not sure I fully understand how the data summation is different from the merge? Clearly data summation allows you more control (arbitrary weighting of groups etc.) and is intended for XANES analysis, but is it a fundamentally different procedure or just a different interface for the same thing?

 

Thanks,

 

Ian

 

 

Ian Godfrey

 

PhD Student,

UCL/JAIST Programme

 

Industrial Doctorate Centre in Molecular Modelling and Materials Science,

Department of Chemistry,

University College London,

 

And

 

School of Materials Science,

Japan Advaned Institute of Science and Technology

 

i.godfrey <at> ucl.ac.uk i.godfrey-8xqbrEIV++l3+QwDJ9on6Q@public.gmane.org

 

02076 794864

 

Attachment (dried.prj): application/octet-stream, 33 KiB
Attachment (dathena.log): application/octet-stream, 993 bytes
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Adi Shivprasad | 25 Jan 18:14 2016
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Re: Ifeffit Digest, Vol 155, Issue 9

Dear all,

Thanks for the quick and informative responses! When I mentioned consistency, I should have clarified that, since I am in the Nuclear Engineering field, the audience for my paper may not have any prior experience with XAS, so I wanted to understand how to explain spectrum features in a way that is accurate and easy to understand from their point of view. To that end, I wanted to make sure I had a better understanding before writing anything incorrect.

Thanks,
Aditya

On Mon, Jan 25, 2016 at 10:14 AM, <ifeffit-request-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org> wrote:
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Today's Topics:

   1. Re: XANES pre-edge vs. edge features (Scott Calvin)
   2. Re: XANES pre-edge vs. edge features (Guanghui Zhang)


----------------------------------------------------------------------

Message: 1
Date: Mon, 25 Jan 2016 10:06:17 -0500
From: Scott Calvin <scalvin <at> sarahlawrence.edu>
To: XAFS Analysis using Ifeffit <ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org>
Subject: Re: [Ifeffit] XANES pre-edge vs. edge features
Message-ID: <9A201B66-AE18-4F10-A367-7E9A7851F705-WZtszHR+tOk@public.gmane.org>
Content-Type: text/plain; charset="utf-8"

Hi Aditya,

Matt gave a good explanation of what?s responsible for the various features, which was part of your question. Another aspect of your question has to do with the way we use terminology.

(Bruce?s answer, and your response, came in while I was writing this. So it may be somewhat superfluous, but since it?s already mostly written, I figure I?ll pass it along.)

As Matt said, ?edge? is a poorly defined term. One meaning of it is that it?s the big rise in absorption that occurs at the start of a XAFS spectrum. That, for example, is the meaning that?s in use when we try to quantify an ?edge step? or an ?edge jump? so that we can normalize the data. In that sense, if a feature occurs before most of that rise, it can be called ?pre-edge.?

But another use of the word ?edge? is as a synonym for ?E0,? which is itself a concept that is not unambiguously defined. One definition of E0 would be ?the energy origin needed to make the EXAFS equation accurate.? But the EXAFS equation is itself an approximation which is only useful at energies starting many eV above E0. So there?s no theoretical reason that the E0 used in EXAFS has to correspond to an energy with a simple theoretical meaning or to any particular feature in the spectrum. The best we can say is that it should be within, or sometimes a bit above, the rising portion of the absorption spectrum.

But when we?re trying to align and process data we need some working definition of E0, both for XANES analysis and to get a preliminary chi(k) for EXAFS analysis. So we come up with other definitions, such as ?the maximum of the first significant peak in the first derivative spectrum.? As Bruce said, the exact definition used is not important, but it is important that the same definition be used with all spectra being compared.

Depending on the definition chosen, the preliminary value of E0 may very well be chosen well below the bulk of the rise in the spectrum. If we call the energy of E0 the ?edge,? but also call features that come before the big rise "pre-edge features,? we end up with the confusing terminology that the edge energy may well be below some of the pre-edge features!

That terminology is unfortunate for people new to the field, but rarely causes any actual ambiguity.

?Scott Calvin
Sarah Lawrence College


On Jan 25, 2016, at 9:40 AM, Matt Newville <newville-Gn9iRbd85Kk2LMHL4Co/2odd74u8MsAO@public.gmane.org<mailto:newville-Gn9iRbd85Kk2LMHL4Co/2odd74u8MsAO@public.gmane.org>> wrote:

Aditya,

The distinction between "edge" and "pre-edge" is not very clear, either when looking at a single spectrum or even conceptually.

In broad terms, the main edge is at the energy where the unoccupied electron levels start - the Fermi energy.   For 1s levels, the transition is to p levels (and for Fe K edge, the 4p level).  So, the main edge is at the energy of the empty 4p levels.   This the transition as being to an atomic level.  In a solid (or liquid), the energy levels above the Fermi level are highly delocalized and spread over many (if not all) atoms in the systems.  Once you get much above the main edge, it's not very easy to assign transitions to identifiable atomic transitions, or even assign a good quantum number to them.

Pre-edge features are generally considered to be unoccupied atomic levels (that is, still assignable to a particular atom, or at least almost so)  below the main edge.   For the transition metal K edges (such as Fe), the main edge is 1s -> 4p.  But Fe has many unoccupied 3d levels.   For a K edge to get to transition to these levels, either you need a quadrupole transition  (unlikely, but not impossible), or (more likely) for bonding/anti-bonding with ligands (typically oxygen) to mix their p-orbitals with the metal d-orbitals.    This hybridization is often called a ligand field or crystal field.    It often gives very identifiable (and at very predictable energies) peaks below the main edge.    Two and sometimes even three peaks can be seen and assigned with ligand field terminology.    There's sort of a whole industry built up around these peaks for transition metal oxides.

These peaks can "leak" into the main edge, and in some cases (say, Cu1+) the classification of "sharp features at the edge" is not very clear.  For Fe metal, it's pretty clear that the main edge (derivative at 7110.75 eV, a small peak on the main edge around 7112.5 eV) is the 4p level, and the rest of the features are actually explainable as EXAFS.

Hopefully, someone will correct anything I got wrong!

--Matt



On Mon, Jan 25, 2016 at 8:13 AM, Aditya Shivprasad <aps202-8DAjSxpRXgY@public.gmane.org<mailto:aps202-8DAjSxpRXgY@public.gmane.org>> wrote:
Dear list,

I was looking at the XANES standard for Fe foil from Hephaestus and I noticed that there was a small, curved feature at the edge (7112 eV), another inflection point at 7116.4 eV, and then the edge step at around 7131 eV. My question is: why is the feature at 7112 eV considered as the edge and not as a pre-edge feature? Are they due to fundamentally different phenomena? I would like to understand where this type of feature comes from so as to be consistent in the current paper that I am writing. I have attached the standard, just in case.

Thanks
--
Aditya Shivprasad

aps202-8DAjSxpRXgY@public.gmane.org<mailto:aps202-8DAjSxpRXgY@public.gmane.org>
Ph.D Candidate
Nuclear Engineering Department
Pennsylvania State University

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Message: 2
Date: Mon, 25 Jan 2016 09:15:41 -0600
From: "Guanghui Zhang" <brighton30-KN7UnAbNpbg@public.gmane.org>
To: "XAFS Analysis using Ifeffit"<ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org>
Subject: Re: [Ifeffit] XANES pre-edge vs. edge features
Message-ID: <4b95e618.1ba7.1527958edcb.Coremail.brighton30-KN7UnAbNpbg@public.gmane.org>
Content-Type: text/plain; charset="utf-8"

Aditya,
Pushkar is correct, and there are several pretty good papers talking about the geometry and pre-edge features of Fe. The following paper is one of them which I found very useful.
http://pubs.acs.org/doi/abs/10.1021/ja964352a

Guanghui




2016-01-25



Guanghui Zhang, PhD
Senior Research Associate
Department of Chemistry
Illinois Institute of Technology
3300 South Federal Street, Chicago, IL 60616
E-mail: gzhang21-WW5Npj40DBY@public.gmane.org; brighton30-KN7UnAbNpbg@public.gmane.org




????pushkar shejwalkar <pshejwalkar2004-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
?????2016-01-25 08:55
???Re: [Ifeffit] XANES pre-edge vs. edge features
????"XAFS Analysis using Ifeffit"<ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org>
???

Dear Aditya,
        Matt has, I think sufficiently explained in details about the pre-edge and its distinction with main energy jump. If my understanding is correct, and it is possible that I may be wrong as well, the pre-edge peak, its appearance shape, intensity and energy value can therefore be used by organometallic researchers to identify and characterize the specific geometry as well. e.g. tetrahedral geometry in Fe (II). By theoretical calculations it is possible to validate such values and thus it is possible to predict the possible geometry of the metal centre (especially with metals like Fe, I used it earlier).
I hope this will be helpful as well.
Pushkar


On Mon, Jan 25, 2016 at 11:40 PM, Matt Newville <newville-Gn9iRbd85Kk2LMHL4Co/2odd74u8MsAO@public.gmane.org> wrote:

Aditya,


The distinction between "edge" and "pre-edge" is not very clear, either when looking at a single spectrum or even conceptually.


In broad terms, the main edge is at the energy where the unoccupied electron levels start - the Fermi energy.   For 1s levels, the transition is to p levels (and for Fe K edge, the 4p level).  So, the main edge is at the energy of the empty 4p levels.   This the transition as being to an atomic level.  In a solid (or liquid), the energy levels above the Fermi level are highly delocalized and spread over many (if not all) atoms in the systems.  Once you get much above the main edge, it's not very easy to assign transitions to identifiable atomic transitions, or even assign a good quantum number to them.

Pre-edge features are generally considered to be unoccupied atomic levels (that is, still assignable to a particular atom, or at least almost so)  below the main edge.   For the transition metal K edges (such as Fe), the main edge is 1s -> 4p.  But Fe has many unoccupied 3d levels.   For a K edge to get to transition to these levels, either you need a quadrupole transition  (unlikely, but not impossible), or (more likely) for bonding/anti-bonding with ligands (typically oxygen) to mix their p-orbitals with the metal d-orbitals.    This hybridization is often called a ligand field or crystal field.    It often gives very identifiable (and at very predictable energies) peaks below the main edge.    Two and sometimes even three peaks can be seen and assigned with ligand field terminology.    There's sort of a whole industry built up around these peaks for transition metal oxides.

These peaks can "leak" into the main edge, and in some cases (say, Cu1+) the classification of "sharp features at the edge" is not very clear.  For Fe metal, it's pretty clear that the main edge (derivative at 7110.75 eV, a small peak on the main edge around 7112.5 eV) is the 4p level, and the rest of the features are actually explainable as EXAFS.


Hopefully, someone will correct anything I got wrong!



--Matt






On Mon, Jan 25, 2016 at 8:13 AM, Aditya Shivprasad <aps202-8DAjSxpRXgY@public.gmane.org> wrote:

Dear list,


I was looking at the XANES standard for Fe foil from Hephaestus and I noticed that there was a small, curved feature at the edge (7112 eV), another inflection point at 7116.4 eV, and then the edge step at around 7131 eV. My question is: why is the feature at 7112 eV considered as the edge and not as a pre-edge feature? Are they due to fundamentally different phenomena? I would like to understand where this type of feature comes from so as to be consistent in the current paper that I am writing. I have attached the standard, just in case.


Thanks
--

Aditya Shivprasad


aps202-8DAjSxpRXgY@public.gmane.org
Ph.D Candidate
Nuclear Engineering Department
Pennsylvania State University


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Best Regards,
Pushkar Shejwalkar.
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Tokyo Engineering University,
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Aditya Shivprasad | 25 Jan 15:13 2016
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XANES pre-edge vs. edge features

Dear list,

I was looking at the XANES standard for Fe foil from Hephaestus and I noticed that there was a small, curved feature at the edge (7112 eV), another inflection point at 7116.4 eV, and then the edge step at around 7131 eV. My question is: why is the feature at 7112 eV considered as the edge and not as a pre-edge feature? Are they due to fundamentally different phenomena? I would like to understand where this type of feature comes from so as to be consistent in the current paper that I am writing. I have attached the standard, just in case.

Thanks
--
Aditya Shivprasad

Ph.D Candidate
Nuclear Engineering Department
Pennsylvania State University
Attachment (Fe.xmu): application/octet-stream, 91 KiB
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Bruce Ravel | 21 Jan 19:37 2016
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Re: Fwd: Citing XANES standards

On 01/21/2016 12:14 PM, Aditya Shivprasad wrote:
> Hi Dr. Ravel,
>
> I am a graduate student in Nuclear Engineering at Penn State. I study
> corrosion of Zr-based alloys using microbeam XANES at the APS. For my
> linear combination fitting of iron XANES spectra I have used your iron
> foil standard that is available through the Hephaestus program. I was
> wondering if there was a paper or work I could cite to reference this
> standard.

Aditya,

I am CCing my answer to the Ifeffit mailing list.  This seems like a 
general enough question that it should go onto the list.

The advice I have given others who have asked this question is to state 
that the standard is distributed with the Demeter software package and 
to use the standard citation for the software.

Cheers,
B

--

-- 
  Bruce Ravel  ------------------------------------ bravel@...

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 535A
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/
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