Abstract
The dynamics of the nuclear magnetic double-resonance process for Na nuclei in a (2,0,0) position relative to a substitutional impurity in NaCl has been studied for several Ag concentrations. The purpose was to determine experimentally the factors which limit the double-resonance sensitivity. For Ag concentrations below 0.03 mole%, the magnetization of unperturbed Na nuclei decayed exponentially with rates proportional to the impurity concentration when a rf field at the resonance frequency of the quadrupole-shifted transitions was applied. Using a method of intermittent search-field irradiation, evidence was found that the finite spin diffusion rate caused a double-resonance energy transfer rate under continuous search-field irradiation about 30% less than the transfer rate which would be observed if the spin diffusion were infinitely fast. A theoretical explanation of the results is given using a perturbation approach based on the concept of spin diffusion. In addition, we have studied the Na spin-lattice relaxation in the completely demagnetized state as a function of impurity concentration, and found a rapid initial decrease of spin order. This was caused by cross relaxation within the nuclear spin system.
- Received 6 October 1969
DOI:https://doi.org/10.1103/PhysRevB.1.2989
©1970 American Physical Society