High Stability Nuclear Magnetic Resonance Spectrograph

Abstract

An NMR spectrograph using an electromagnet is superstabilized by a feedback loop which uses the error signal from a secondary nuclear resonance probe to control the oscillator driving frequency. Field fluctuations thus produce such frequency variations as to preserve the Larmor condition for both short and very long times. The same oscillator is used for the measurement probe and thus also the Larmor condition is preserved in the sample being measured. Means are provided for sweeping frequency to produce precalibrated spectra of high precision at various magnifications and scale shifts with a very convenient and rapid setup procedure. Frequency scales are directly related to graph paper markings. Improved temperature control of the magnet and a reproducible precycling recipe also contribute to an unusually high degree of stability and reliability of day-to-day operation.