Alignment of Cerium-141 and Neodymium-147 Nuclei

The radioactive nuclei Ce141 and Nd147 have been aligned by the magnetic hfs method (Bleaney) using single crystals of cerium magnesium nitrate. The cerium site is characterized by B≫A, i.e., the "alignment" occurs in a plane. The anisotropies for the 142-kev gamma ray of Ce141, and the 92-kev and 530-kev gamma rays of Nd147, at the lowest temperature (0.00308°K) were found to be +0.12, 0, and -0.39, respectively. These values coupled with the rate of change of anisotropy with temperature identify the transitions as M1, M1+E2, and E2, respectively. The decay schemes supported by these experiments are as follows: Ce141 (142 kev), 72−−0→72+−1→52+; Nd147 (92 kev), 92−−1→72+−1,2→52+; Nd147 (530 kev), 92−−0→92+−2→52+. From the temperature dependence of the anisotropies we can deduce values for the magnetic moments as follows: Ce141, 0.16±0.06 nm; Nd147, 0.22±0.05 nm. These rather small values for odd-neutron nuclei may not be meaningful because of possible internal magnetic field effects in the crystal which are not taken into account in the treatment of the hyperfine interaction.