Capture of Polarized Neutrons by PolarizedSm149Nuclei

Abstract

The ${\mathrm{Sm}}^{149}$ nuclei in the paramagnetic salt, samarium ethyl sulfate, were polarized by use of the hyperfine structure coupling, which was known to be large from paramagnetic resonance measurements. The Sm salt was placed in a field of 11 000 gauss after being cooled by thermal contact with a sample of iron ammonium alum which was demagnetized to zero field from 15 500 gauss and 1.2°K. The nuclear polarization was observed and measured by observations on the state of polarization of the neutrons transmitted by the Sm sample. A single crystal of magnetized magnetite, set to reflect neutrons of 0.07 ev in first order from the 220 planes was used as the analyzer. A nuclear polarization of about 0.12 was deduced from the data. The observed polarization direction of the transmitted neutrons gives $J=I+\frac{1}{2}$ for the 0.094-ev resonance level in ${\mathrm{Sm}}^{149}$. A temperature of about 0.13°K for the Sm-containing salt was deduced from the observed neutron polarization.