A high-field/high-frequency heterodyne induction-mode electron paramagnetic resonance spectrometer operating at 360 GHz

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Abstract
We present design details of and first measurements with a novel continuous wave (cw) high-field/high-frequency electron paramagnetic resonancespectrometer operating at a microwave frequency of 360 GHz and a magnetic field of up to 14 T. The spectrometer design incorporates a heterodyne mixer detection scheme with a quasi-optical transmission line and a bimodal induction mode Fabry–Perot cavity. First cw experiments on polycrystalline 1,1-diphenyl-2-picryl-hydrazyl and bisdiphenylene-β-phenylallyl benzolate in polystyrene at room temperature and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl in frozen solution at 190 K demonstrate the high Zeeman resolution achievable and allow an estimate of the present detection sensitivity of 4×10 9 spins/G at a detection bandwidth of 1 Hz.