Comparison of crystals for oxygen analysis

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Abstract
A comparison is made between five acid phthalates and clinochlore as analyzer crystals for oxygen Kα emission. Thallium acid phthalate (TAP) is shown to be superior for quantitative analysis because it has high reflectivity, relatively smaller corrections to reflectivity for anomalous dispersion, relatively low high order reflectivities and relatively low fluorescence background. The interplanar 2d spacing for TAP is 25.7626 ± 0.001 Å and its coefficent of thermal expansion α is 32.7 ± 1 K−1. At the oxygen Kα position its effective 2d spacing is 25.724 Å and the mean reflection coefficient is 2.8 × 10−4 rad. For analysis of chemical state, where higher resolution is often desired to distinguish band shapes and satellites, rubidium acid phthalate (RAP) is the best choice. It has α = 37.0±3 K−1, an effective 2d spacing of 26.083 Å and a mean reflection coefficient of 8.2 × 10−5 rad.