Alignment of Cerium-141 and Neodymium-147 Nuclei

The radioactive nuclei ${\mathrm{Ce}}^{141}$ and ${\mathrm{Nd}}^{147}$ have been aligned by the magnetic hfs method (Bleaney) using single crystals of cerium magnesium nitrate. The cerium site is characterized by $B\gg A$, i.e., the "alignment" occurs in a plane. The anisotropies for the 142-kev gamma ray of ${\mathrm{Ce}}^{141}$, and the 92-kev and 530-kev gamma rays of ${\mathrm{Nd}}^{147}$, 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 $M1\mathrm{}$, $M1+E2\mathrm{}$, and $E2\mathrm{}$, respectively. The decay schemes supported by these experiments are as follows: ${\mathrm{Ce}}^{141}$ (142 kev), $\frac{7}{2^{-}}{-}^0\to \frac{7}{2^{+}}{-}^1\to \frac{5}{2^{+}}$; ${\mathrm{Nd}}^{147}$ (92 kev), $\frac{9}{2^{-}}{-}^1\to \frac{7}{2^{+}}{-}^{1,2}\to \frac{5}{2^{+}}$; ${\mathrm{Nd}}^{147}$ (530 kev), $\frac{9}{2^{-}}{-}^0\to \frac{9}{2^{+}}{-}^2\to \frac{5}{2^{+}}$. From the temperature dependence of the anisotropies we can deduce values for the magnetic moments as follows: ${\mathrm{Ce}}^{141}$, 0.16±0.06 nm; ${\mathrm{Nd}}^{147}$, 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.