Applying for beamtime at the AS MEX1 and MEX2 beamlines

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If you answer “NO” to any of these questions; STOP.  Go back and take the necessary steps to answer “YES”, otherwise your proposal is likely uncompetitive.

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Sample table template showing filled-out example for your convenience – modify Present below is an example sample table. You may copy and paste this into your proposal and modify to suit your experiment. Concentration is particularly important for the beamline team to determine feasibility. Failure to provide an appropriate concentration increases the chances your experiment will be deemed infeasible. For fluorescence (‘F’) and drain current (‘D’) experiments, please express concentrations in either wt.%, ppm or mM. Metal loadings in mg are not concentrations. For transmission experiments (‘T’), please report both the edge step (Dmd) and total absorption 50 eV above the edge (mt). Weight percent, ppm or molal are not valid concentrations for transmission experiments. You can conveniently calculate edge steps and total absorption using the XAFSmass freeware by Konstantin Klementiev); for instructions see here).

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Sample

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Edge

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Furthermore, it is vital you know the composition of your sample if you want to make a successful x-ray absorption spectroscopy measurement. The way you present concentration in the sample table depends on the analysis mode (fluorescence, F; transmission, T; or drain current, D) you wish you use:

• Fluorescence - express the concentration of the element of interest in one of the following units:

  • weight percent

  • part per million (ppm)

  • millimolal (liquid samples only)

  • samples measured in fluorescence are susceptible to over absorption (also referred to as self-absorption). Good fluorescence samples have 2000 ppm or less of the element of interest. If your samples have weight percent abundance, you will have to dilute them, or develop a strategy for correcting for self-absorption.

• Transmission

  • edge step (Δμd) and total absorption (μd)

  • it is vital you understand the composition of your sample, and the properties that make a good transmission sample. See this comprehensive guide for how to calculate the appropriate dilution for transmission samples in pellet form.

• Drain current - express the concentration of the element of interest in one of the following units:

  • weight percent

  • part per million (ppm)

A common mistake seen in proposals from the catalysis community is to report metal loading in the concentration column. A metal loading is not a concentration. Metal loadings do not help the beamline team assess whether your samples are appropriate for x-ray absorption spectroscopy measurements, but do communicate that you have failed to read this guide. Knowing only the metal loading also rarely helps you, the user, to prepare appropriate samples. If you do not know the exact composition of your sample, you are going to have to develop a strategy to produce samples which give you an opportunity measure good data. That may involve preparing the same material at a range of dilutions to cover the possible range of concentration of the element of interest. If you do not know your composition, and your amount of sample is limited, your experiment is likely to be difficult.

Outcome of previous Australian Synchrotron experiments (past 3 years)

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