Abstract
Measurements have been made of the polarization of the recoil nuclei resulting from the reaction for in the range 0.90 to 3.20 MeV. The polarization is observed by measuring the -decay asymmetries of the recoil nuclei with respect to the reaction plane. The recoil nuclei formed in the ground state are separated kinematically from those in excited states and are then stopped in various solids in the presence of a small magnetic field normal to the reaction plane. The sign of the observed polarization for all measurements is in the direction of the vector . The magnitude of the polarization is strongly dependent on , the recoil emission angle and the material used to stop the recoils. It is found that the polarization of nuclei can be maintained in either metallic Pd or Au at room temperature, using holding fields smaller than 20 G. For recoils stopped in Pt metal, a magnetic field of about 200 G is required to maintain the nuclear polarization. The recoil polarization plotted as a function of shows definite structure. Polarization resonances are observed at 1.5, 2.1, and 3.0 MeV. At these energies the measured relative polarizations are +(8.01±0.30)%, +(4.29±0.30)%, and +(3.86±0.27)%, respectively, for a Pt metal recoil stopper and a 49° (lab) recoil angle. These resonances are tentatively identified with states of the compound nucleus near 20.0 MeV and at 20.52 and 21.28 MeV. It is believed that the polarization resonances may result from an interference between direct interaction and two-particle compound resonance processes.
- Received 13 July 1967
DOI:https://doi.org/10.1103/PhysRev.163.999
©1967 American Physical Society