The Split Pea™ Hemi Micro ATR Sampler has the smallest sampling area of any ATR accessory. The hemispherical optic design is well matched to the refractive indices of the crystal materials and results in concentration of the beam by a factor equal to the refractive index of the material (3.4 for Si and 2.4 for diamond), thereby minimizing stray light and shrinking the sample area. The small sample area – 250 µm for a Si crystal and 500 µm for a diamond crystal – translates into easier alignment of small samples in the beam and the ability to apply localized pressure to the sample thereby improving contact between the sample and the crystal at high pressures. Furthermore, the hemispheric optics do not cause the beam to defocus after it strikes the sample as occurs with conventional prisms used in internal reflection spectroscopy. (see Diagram) The result is enhanced spectral resolution with small and irregular samples.