Abstract

New cell geometries for extending the dynamic range of FT-IR absorption spectroscopy are described. These are variants of the stepped multiple thickness cells described before, in which the cell thickness varies continuously with location. Either homogeneous wedge or lenslike cells are used. The resulting distortion of the cell's photometric linearity can be straightened out computationally. However, the change in the measured energy levels drastically increases the dynamic range of the measurement for a given tolerable relative error in absorbance. The theoretical behavior of the cells is analyzed, and their photometric distortion and dynamic range calculated. The experimental realization of one of them is used to show the usefulness and limitations of the procedure.

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