Optical Detection of Magnetic Resonance in Alkali Metal Vapor

Abstract

This paper discusses two types of rf magnetic resonance experiments involving optical pumping in alkali vapor which have recently been suggested by Dehmelt. These experiments are, respectively, observation of a change of intensity at resonance of the transmitted pumping light, and observation of high-frequency intensity modulation in a second light beam (the "cross beam") incident at an angle to the first. The method of pumping used here is reviewed, together with some of the special assumptions on which it is based. The function of the light in monitoring population differences is treated as a separate matter from the pumping function; it is shown that the observed changes in transmitted light intensity can be correlated in a simple way with other observables of a spin system, and this leads to a simple explanation of the high-frequency modulation effects. A system of spin-\textonehalf{} particles subject to optical pumping and monitoring is then treated phenomenologically. The resulting equations have the same form as Bloch's equations except that (1) the time constants must include effects of the incident light, and (2) there is an additional term due to the cross beam which, however, is shown to have no effect on the shape of the resonance.The apparatus is described, together with experimental conditions under which signals have been observed. Possible applications of the technique include magnetic-field measurements, and studies of atomic constants of alkali metal isotopes.