Sensitivity Considerations in Microwave Paramagnetic Resonance Absorption Techniques

This paper discusses some factors which limit the sensitivity of microwave paramagnetic resonance equipments. Several specific systems are analyzed and the results verified by measuring the signal-to-noise ratio with known amounts of a free radical. The two most promising systems, especially at low powers, employ either superheterodyne detection or barretter homodyne detection. A detailed description of a superhetrodyne spectrometer is given.