Radiation-detected optical pumping in solids

Abstract

Radiation-detected optical pumping in solids has been developed to investigate the structure of unstable nuclei. Appreciable nuclear polarization of implanted or doped unstable-nuclei in a host crystal is achieved with the optical pumping in solids. The nuclear polarization achieved is enhanced/reduced by applying a radio-frequency magnetic field together with the optical pumping, radiation-detected magnetic resonance being thus observed to get information on electromagnetic properties of unstable nuclei. Two schemes have been successfully developed for the optical pumping of unstable nuclei in solids. One is to directly pump the atoms by the excitation from the ground state to a broad absorption band in visible and UV regions which shows a large magnetic circular dichroism. This scheme is applicable to many rare-earth atoms in alkaline-earth fluoride host. The other scheme is to pump the electrons in the conduction band of direct-type semiconductor and thus indirectly polarize the nuclei in the host material via a hyperfine interaction between the nuclei and the polarized conduction electrons. This scheme can be especially applied to the III to VI families of atoms in direct-type semiconductors. Principle of the methods, on-line experimental system, and a few examples of the results obtained so far are presented and discussed.