Spin Assignments of Low-Energy Resonances Using Polarized Neutrons and PolarizedSm149Nuclei

Abstract

The spins of the four resonances at 0.0976, 0.87, 4.93, and 8.9 eV in ${\mathrm{Sm}}^{149}$ have been measured by using a monoenergetic polarized neutron beam incident on polarized samarium nuclei. By using one stage of adiabatic demagnetization, polycrystalline samples of samarium ethyl sulfate and samarium double nitrate were cooled to approximately 0.15°K. At this temperature and with the aid of an external magnetic field an appreciable polarization of the samarium nuclei is achieved by making use of the hfs coupling (Rose-Gorter method). The spin assignments for the above four resonances were all $J=I+\frac{1}{2}=4\mathrm{}$. The samarium nuclei in the double nitrate sample were found to be polarized in the same direction as in the ethyl sulfate sample. Measurements made on samarium metal at these low temperatures indicate that it is antiferromagnetic.