Spin-Exchange Optical Pumping of Solid Alkali Compounds*

Spin-exchange optical pumping of noble gases has been used for many years to create highly non-equilibrium spin populations, with applications ranging from fundamental physics[1] to medical imaging[2]. In this procedure, angular momentum is transferred from circularly-polarized laser light to the electron spins of an alkali vapor and ultimately to the nuclei of a gas such as $^3$He or $^{129}$Xe. Here we show experimentally that a similar process can be used to polarize the nuclei of a solid film of cesium hydride which coats the walls of an optical pumping cell. We present nuclear magnetic resonance (NMR) data which demonstrate that the nuclear polarization of $^{133}$Cs in CsH can be enhanced above the Boltzmann limit in a 9.4-Tesla magnetic field. Possible spin-exchange mechanisms will be discussed, as well as the extension of this technique to other compounds. \newline [1] T.~W.~Kornack, R.~K.~Ghosh, and M.~V.~Romalis, Phys. Rev. Lett.~\emph{95}, 23080 (2005). \newline [2] M.~S.~Conradi, D.~A.~Yablonskiy, et al., Acad. Radiol.~\emph{12}, 1406 (2005).