This is an external transmission and reflectance sample chamber that can be mated to the output port of both the SPS-200 and SPS-300 FTIRs. This sample chamber allows small samples such as liquid in a cuvette or thin films to be studied under both transmission and reflection modes. The sample chamber is totally isolated from the SPS-200/SPS-300 vacuum environment by a sealed polyethylene window at its input port (output port of the SPS FTIR), and thereby enabling the user to change samples without upsetting the SPS-200/SPS-300 vacuum housing. The sample chamber can be operated independently in vacuum (optional upgrade) or in atmospheric conditions. The sample chamber utilizes reflective aspheric optics with gold coating for far infrared and terahertz operation. A manual flipping mirror inside the sample chamber allows the user to select between transmission and reflective modes. In transmission mode, an internal mirror focuses the sample onto the detector, whereas in reflection mode, a secondary internal mirror focuses onto the sample. All optics are pre-aligned and focused for a specific detector positions at the sample chamber output port. An optional peltier cooler is also available to maintain the temperature of the sample holder. For this option, a water cooling loop inside the sample chamber is required. This water cooling loop can be connected to the same water re-circulating system as the main SPS-200/SPS-300 body or though a separate independent cooler such as the Sciencetech Model 160-REC water recirculator. Anumber of custom made sample holders can be supplied as options.