In 1948 NRC invited Dr. Gerhard Herzberg to establish a laboratory for fundamental research in spectroscopy, and under his leadership NRC became a World leader in this field.
This apparatus was built for Herzberg and put into operation in 1950. It is not very different from a standard spectrograph, in that it allows for a source of light (usually emission tubes filled with the gases to be studied), gratings to produce the spectra of the light, and a camera to record the spectrum. The main difference is that the entire cavity can be evacuated to very low pressures allowing work in regions of the electromagnetic spectrum (such as the ultraviolet) where air absorbs the radiation. Previously, molecules whose characteristic spectra were in this region could not be studied spectroscopically.
With this apparatus Herzberg was able to determine precisely the structures and properties of free radicals, most notably CH2 (methylene) a molecule whose spectral lines had previously been detected but unidentified in space. The short lived spectral lines of CH2 were first recorded in this instrument in 1959 and led to Herzberg’s Nobel Prize for Chemistry in 1971.