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

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/Beamlines/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:

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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

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-- Best Regards, Pushkar Shejwalkar. Post-doctoral -Researcher, Tokyo Engineering University, Tokyo-to Japan

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