Knowledge Bank

A high resolution spectrometer has been designed to operate in the wavelength region spanning the near infrared through the visible. The monochromator configuration is a 1 1/4 meter Ebert-Fastie. The grating is a Bausch and Lomb $5\times 10$ inch, 316 groove per millimeter echelle driven by a programmable stepping drive. A Perkin Elmer Model 112 spectrometer equipped with a $CaF2$ prism has been modified to act as a predisperser. The sample section follows the monochromator so that only the highly dispersed light excites the sample gas. An interesting feature of the sampling section is the method of double beaming. A beam flipping mirror shifts the sample beam through two paths to a single detector. The signal from the detector [lead sulphide or photomultiplier] is amplified and digitized by an $A/D$ converter and then routed by a PDP-11 computer system to a storage buffer. Design features and performance will be discussed.