Re: [Ifeffit] Calculation of metal concentration (and hence density) from Edge Jump

27 Feb 2017

      Dear Pushkar,

1) µ is the total absorption at a given energy. If you are above the edge,
it will be higher than if you are below. Test it by changing the energy.
NOTE that the absorption value you have in Athena is calculated form the
ion chamber values, which are amplified. If I2 is amplified 10x higher than
I1, -log(I2/I1) will be -log(10) = -1, i.e. lower by 1 relative to the real
value. Knowing the amplification factors, you can take this into account.
2) yes. Athena determines it for you during normalisation. It is the
difference between the pre-edge and post-edge fit curves at the position of
E0. This is the proper way of determining the edge step.
3) yes. This is a statistical thing. Try to normalise using different
ranges and you will get slightly different values of Delta µ. The standard
deviation you can give as delta µ. If the uncertainty does not interest
you, you can probably set this value to 0.

Hope this helps.
Alexey

2017-02-27 5:56 GMT+01:00 pushkar shejwalkar :
...
Dear Alexey,
      Thank you for your insightful suggestions and very useful
information. Now that I have got the XAFSmass program running (?) it is
giving me some values and no more error. So I am assuming that I am doing
everything right. However, I still have some questions regarding the
READING and UNDERSTANDING of the data input and output from the program.
From the manual, it is not very clear and difficult to understand some of
the input values. In the unknown concentration tab
1) u = high u?? meaning highest absorption?
2) DELTA ud is = to deltaU i.e. typically what we get as edge step in
Athena??
3) deltaut = uncertainty?
For the novice learner like me could you please tell me how exactly can we
calculate these values from the single spectra (preferably). I am aware of
the crude ways to find it but would like to more proper and scientific way.
By the Way, in order to establish these values, should we use the crude
data file or properly processed data file e.g. K-weight corrected,
background adjusted, aligned and calibrated data?
Sorry for the inconvenience and thank you very much in advance for the
details.
Sincerely yours
Pushkar
On Thu, Feb 23, 2017 at 6:18 PM, Alexey Boubnov 
wrote:
...
Dear Pushkar,
1) M%x is the mass percentage.
2) This function is for calculating the element concentration from the
absorption spectrum. XAFSmass does not have problems with long formulas.
You wrote the formula correctly, but maybe you did not indicate also the
total absorption, edge jump with uncertainty and energy?
All the best.
Alexey
2017-02-23 2:54 GMT+01:00 pushkar shejwalkar :
...
Thank you, Alexey, for very useful information. Currently, I am working
on XAFSmass. Technically it looks much more flexible than the software
provided by SPring-8 since almost all the variables can be changed and
adjusted as per the requirements.
1) However, sample information is very tedious to put in and confusing
as well. Do you happen to know what exactly does M%x (is this mass % or
mole %).
2) I am working on the tab with the determination of unknown
concentration Label and I am interested in finding out the Fe concentration
only. So I should write Fe%x (I assume). However, since I use
organosilica's the formula is not so straightforward. My empirical formula
for the catalyst is FeC580H382O152Si98N10F6S2. Do you think the program can
handle such information? I wrote Fe%xC_580H_382O_152Si_98N_10F_6S_2.
But it is giving an error that 'can not calculate concentration'. Am I
doing something wrong?
I have already read the pdf in the software and as such it looks not so
complicated but just the syntax of writing chemical formula is different
and con-conventional.
Sincerely yours
Pushkar
On Wed, Feb 22, 2017 at 9:52 PM, Alexey Boubnov 
...
wrote:
...
Dear Pushkar,
regarding your last question: the absorption edge jump (Delta µd) is
the difference in absorption before the edge and after the edge, e.g. Pt
L3-edge is at 11564 eV, so Delta(µd) = µd at 11580 eV - µd at 11550 eV. The
total absorption (µd) takes all atoms into account. You only need the
difference. I and I0 do not contain information on the sample, so they are
useless for this purpose.
Regarding your original question (calculation of the edge jump knowing
the composition of your sample): there are programs available to calculate
the edge jump and amount of sample from the composition and total
absorption, saving you the effort with formulas and letting you focus on
your sample. Try XAFSmass (https://intranet.cells.es/Bea
mlines/CLAESS/software/xafsmass.html).
Here you can enter the bulk composition (e.g. Fe%10SiO_2 for a silicate
with 10% Fe-content), energy (e.g. slightly above Fe K-edge: 7150 eV),
pellet area (e.g. 1.3 cm²), total absorption (e.g. µd = 1) and press
"calculate". This gives you the mass of your sample (e.g. 12 mg
[hypothetical value]) and the edge jump due to the Fe K-edge (e.g.
Delta(µd) = 0.2 [hypothetical value]). The mass and edge jump are
approximately proportional. Consequently if your pellet in reality contains
60 mg iron silicate (5x the calculated number), absorption values will also
scale: Delta(µd) = 1.0 and µd = 5, which is a little too high. Play around
with the value of µd in the program to see the effect on mass and edge jump.
I wish you successful calculations and experiments!
Alexey
2017-02-22 5:54 GMT+01:00 pushkar shejwalkar 
...
:
...
Thank you, Bruce and Alexey for your kind information.
Bruce the communication, unfortunately, is not available on our
Internet connection from university to download for free. Do you think it
would be possible (under the copyrights act off course) for you send a PDF
copy? The communication seems really interesting and I will keep the
procedure in mind (for March Dates when we have BL for us again) to make
sure that we have a calibration curve. (off course XRF is more reliable and
easy).
Alexey, I read the section (also some other information in that book).
The book is really great. Thanks for sharing.
I have already sat down with the pen and paper. but just want to know
one thing. Is Edge Jump = Absorbance?? or we need to calculate the
absorbance by actually practically finding out the I and Io?
e.g. if edge jump = absorbance I can modify the equation I = Io^e-upd
into its A form. If not I will use ion chamber gas ratio to calculate the I
and Io respectively.
Which way is more correct?
Best Regards
Pushkar
On Tue, Feb 21, 2017 at 10:15 PM, Bruce Ravel  wrote:
...
This might help: https://doi.org/10.1107/S1600577514001283
Note that we measured a sequence of standards of known thickness and
concentration /prior/ to the rest of the experiment, so the methodology in
that paper might not be useful after the fact in the absence of that prep
work.
B
On 02/20/2017 10:19 PM, pushkar shejwalkar wrote:
> Dear All,
>     First of all, is it possible to calculate the concentration of
> metal
> (loading, therefore) from just the edge jump? Is there a simpler
> equation like knowing the Flux values or some basic instrumental
> information we can calculate the concentration term using Io and It
> values of beamline (the simplest form of Beer-lambert law)? if so
> what
> formula should we use.
> I searched in the mailing list archive and have found one such
> archive
> but it discusses how to use calculation to find out how much sample
> would be needed to get the edge jump. I am rather interested in the
> reverse way. I have an experimental edge jump and want to calculate
> (if
> possible with as much accuracy as possible) the concentration of
> metal.
> I know with only edge jump it will be difficult and XRF will be a
> better
> and more reliable way. But for better understanding and cross
> checking
> between different samples, I wish to do such calculations.
> Can anyone guide me to the right direction and equations to do such
> calculations?
> Thank you all in advance
> Warmest regards
> Pushkar
>
> --
> Best Regards,
> Pushkar Shejwalkar.
> Post-doctoral -Researcher,
> Tokyo Engineering University,
> Tokyo-to
> Japan
>
>
>
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--
 Bruce Ravel  ------------------------------------ bravel@bnl.gov
National Institute of Standards and Technology
 Synchrotron Science Group at NSLS-II
 Building 743, Room 114
 Upton NY, 11973
Homepage:    http://bruceravel.github.io/home/
 Software:    https://github.com/bruceravel
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Best Regards,
Pushkar Shejwalkar.
Post-doctoral -Researcher,
Tokyo Engineering University,
Tokyo-to
Japan
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Best Regards,
Pushkar Shejwalkar.
Post-doctoral -Researcher,
Tokyo Engineering University,
Tokyo-to
Japan
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Best Regards,
Pushkar Shejwalkar.
Post-doctoral -Researcher,
Tokyo Engineering University,
Tokyo-to
Japan
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