Millimeter electric resonance spectroscopy

A description is given of a molecular beam apparatus which extends electric resonance spectroscopy into the millimeter wavelength region. Interferometer techniques are employed to achieve high resolution of molecular rotational transitions. With the Ramsey double resonance technique, linewidths as narrow as 350 c/s have been attained for a hydrogen sulfide rotational transition at 168.7 Gc/s. Observations have been made as high as 216 Gc/s, and, with the methods described, the spectrometer can be used in the submillimeter wavelength region.