A DOUBLE MAGNETIC FIELD MODULATION PARAMAGNETIC RESONANCE SPECTROMETER

Abstract

A high sensitivity, wide or narrow band, double magnetic field modulation type paramagnetic resonance spectrometer operating at a wavelength of 1.25 cm. for use at liquid helium temperatures (4 °K.) is described. The spectrometer employs a transmission type, cylindrical resonant cavity excited in the H₁₁₁ mode. The magnetic field is modulated simultaneously at 60 c.p.s. and 465 kc. A resonance from 10⁻¹¹ mole of diphenyl trinitro phenyl hydrazyl has been observed with a signal-to-noise ratio of 2:1 at 290 °K. in wide band operation (8 kc.) indicating that a sensitivity of O(10⁻¹⁵) mole should be possible in narrow band operation (1 c.p.s.) at 4 °K. because of its inherent high stability.