Macroscopic Dipole Coherence Phenomena

Abstract

A review of early developments in NMR research would give an account of numerous effects involving coherent magnetic field-dipole interactions that play a common role today in the understanding of coherent laser phenomena. When the Bloch and Purcell groups initiated the science of NMR, it was not anticipated then or for a number of years afterward that the dynamics of NMR could be applied to electric dipole resonance transitions. The concepts of spin states dominated the interests of investigators because of the tradition of the the Rabi atomic beam method and because radio frequency techniques were ripe for application. In NMR and EPR research, curiosity was and still is focused upon lineshape and spectral structure analysis, where the spins act as probes of the medium. Because the applied field energy usually far exceeds total spin coupling energies, applied fields are taken as constant, and the role of cavity coupling in the equations is not considered under this restriction. The dynamics of the field intensity variations themselves therefore cannot become evident. This restriction was removed with the advent of maser-laser principles.

Supported by the National Science Foundation.