Attenuated total reflection crystal fabricated from diamond material

An attenuated total reflection (ATR) crystal for ATR spectroscopy of a sample to be analysed,

• the ATR crystal being formed of a diamond material, and
• configured to have an inlet surface for an infrared analysis beam, an outlet surface for the infrared analysis beam, and a working surface for contacting the sample to be analysed, wherein the ATR crystal is in the form of a chamfered cylinder comprising two flat chamfered side walls forming the inlet and outlet surfaces, and an end surface of the chamfered cylinder forming the working surface;
• the inlet surface, the outlet surface and the working surface being configured such that in use the analysis beam can be directed through the inlet surface to an inner side of the working surface in contact with the sample to be analysed and internally reflected at the inner side of the working surface in contact with the sample to be analysed such that the analysis beam passes out of the ATR crystal through the outlet surface, and
• characterized in that the working surface is convexly curved, wherein the convexly curved working surface defines a segment having a depth in a range 2 to 100 μm.