A microwave-switched time integration (MISTI) method in the study of spin-polarized radicals

Abstract

An experiment is described in which polarized free radicals are created in a laser pulse in the absence of a microwave field which is applied at a later time in a continuous wave fashion. In this way the periods of evolution and observation of the magnetization are separated in a two-dimensional experiment. Analysis shows that the variation in the observed time-integrated signal with the evolution period gives the electron spin-lattice time directly. A simple corollary yields the polarization ratio. Comparison is made with more conventional methods for determining these quantities. A further new method is described for determining the polarization ratios of all hyperfine components in a spectrum simultaneously using time-integration spectroscopy(TIS).