Radiofrequency Spectroscopy Using Three-Level Maser Action

A direct transition between l -type doublet of OCS molecule was observed either as emission or absorption using the three-level maser action. The pumping radiation was supplied by a klystron 2K33 at the frequency correspanding to J =2←1, and the l -type doubling transition at 12.78 Mc/sec for J =1 was observed by a modified Pound-Knight circuit. Generally the low frequency transition of molecules is shown to be detectable using the bandwidth of about 1 s -1 , if the corresponding microwave transition at 24,000 Mc/sec has the absorption coefficient larger than 10 -8 cm -1 . The line-width can possibly be reduced to several kc/sec at the sacrifice of sensitivity. The application of this type of spectrometer is also discussed.