A novel geometry for internal reflection elements is described. These elements have been found most useful in the FT-IR analysis of samples by attenuated total reflectance (ATR). Both single and multiple internal reflection elements are described. These elements provide three basic benefits. First, the geometry is such that an element may be exchanged for another of differing angle of incidence without the need for optical realignment of the sampling accessory. Second, for a given element thickness and width, the design allows a larger aperture over the conventional designs (parallelograms and trapezoids) for angles of incidence greater than 45 degrees, resulting in better sensitivity. Third, the elements are of a simple design, and are easy to fabricate.
Robert G. Messerschmidt, "A New Internal Reflection Element Design for High Optical Throughput in FT-IR," Appl. Spectrosc. 40, 632-635 (1986)