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 BA, 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.