Magnetic Double Resonance Spectrometer for Dynamic Nuclear Polarization and Relaxation Time Measurements at 175 G

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Abstract
A magnetic nuclear‐electron double resonance spectrometer operating in magnetic fields of about 175 G is described. It is suited for measurements of dynamic nuclear polarization and relaxation times in proton and fluorine containing solvents. The NMR spectrometer is a Q‐meter device synchronized by a crystal oscillator. The uhf setup for the saturation of the ESR lines consists of a frequency multiplied driver stage and a 493 Mc power stage. The sample is placed inside a quarter wavelength coaxial cavity with the NMR coil around it. A rapid modulation technique allows u‐mode detection and convenient comparison of NMR signals with and without ESR irradiation. The nuclear relaxation times (T2) are measured by observing the decay of the magnetization brought into the x,y plane by an adiabatic passage in the presence of a strong rf field. The performance is demonstrated with examples of proton polarization studies in organic solutions of free radicals.