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Edge step/absorptance step: The magnitude of the change in absorption as a monochromatic beam is scanned across an absorption edge. Only atoms of the element corresponding to the absorption edge contribute to the edge step. The size of the edge step is proportional to the concentration of the element of interest in the sample. Edge step is expressed in absorption units.
MEX1 can measure edge steps down to 0.1 without problem. Close to 1 is ideal, 0.01 means the sample is probably better suited to fluorescence.
Optical thickness: In this guide, optical thickness refers to how absorbing a material is, expressed in absorption units. e.g. "My sample has an optical thickness of 2.3 absorption units". Optical thickness and total absorption can be used interchangeably.
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