A saturation effect spectrometer

This paper describes a microwave spectrometer technique which utilizes the nonlinear properties of resonance saturation in gases for the detection of absorption lines. An outline of the principle of detection which relies on the automatic balance of a resonant bridge is given, and methods of measuring line widths and relative intensities are obtained from a comprehensive analysis of the spectrometer output signal. The problem of sensitivity is examined, and some of the advantages of extending the technique to millimeter waves are indicated. A K-band saturation effect spectrometer has been constructed which exhibits a sensitivity of the order of 10^-9cm^-1with a resolution better than 100 kc/s.