Knowledge Bank

An infrared grating spectrophotometer has been built for the direct recording of infrared transmittance vs. wavelength. Using a fore prism and a mosaic of four replica gratings, $5\prime \prime \times 7\prime \prime$, it is capable of unusually high resolution with freedom from noise and scattered light. Any one of the first five orders of the grating may be used by electrically synchronizing the prism with it and programming the slits for constant energy. The choice of resolution, scanning speed, and response time may be varied within very wide limits. Single-beam and double-beam operation and single pass and double pass of the grating section are all possible. Other features include the possibility of substituting external sources and detectors, space for a wide variety of absorption cells, and an all-electric control system. The design, construction, and performance of the instrument will be discussed.