Recording High-Sensitivity Paramagnetic Resonance Spectrometer

Abstract

A high-sensitivity, automatic recording paramagnetic resonance absorption spectrometer operating at a wavelength of 3.2 cm is described. The spectrometer is of the crystal-heterodyne type employing a local-oscillator and a magic tee bridge with a reflection cavity. Automatic frequency control of the signal and local-oscillator klystrons is provided to eliminate anomalous dispersion and to reduce frequency fluctuations. The output signal can be presented as a trace of the paramagnetic absorption versus magnetic field on a continuous strip recorder, as a pattern on an oscilloscope of absorption versus magnetic field for either visual observation or photographic recording, or as a continuous recorder trace of the derivative of absorption versus magnetic field. Provision is made for calibration of the magnetic field by means of the proton magnetic resonance absorption. Approximately 2×10−11 mole of 1, 1-diphenyl-2-picryl hydrazyl can be detected with the spectrometer.