Rotating-Frame Nuclear-Double-Resonance in NaCl: Spin-Calorimetry and Multiple-Spin-Flips

Abstract

An experiment of the nuclear double resonance in the rotating frame is carried out on Na²³–Cl³⁵ system in a single crystal of NaCl. The double resonance signals caused by one sodium spin flip accompanied by two chlorine flips, and by one chlorine flip accompanied by two sodium flips are observed, in addition to the ordinary signals caused by one sodium and one chlorine flips. The experimental results are analyzed from the viewpoint of thermodynamics (spin-calorimetry) and an effect of Cl³⁵ spin-lattice relaxation on the double resonance is taken into account. The spin-lattice relaxation time of Cl³⁵ is measured indirectly by using the double resonance spectrum obtained. In addition, a sensitive technique, available in the NMR experiments in solids, is developed to adjust a static field to a resonant value for a given rf frequency.