Nuclear levels of ${\mathrm{Dy}}^{163}$ have been investigated, combining the following experimental techniques: the measurement of low-energy ($n, \gamma$) radiation between 30 keV and ≈1.2 MeV using a curved-crystal spectrometer, the measurement of ($n, e^{-}$) conversion electrons in the energy range between 113 and 950 keV with a double-focusing $\beta$ spectrometer, the investigation of high-energy ($n, \gamma$) transitions between 4 and 6.4 MeV using a Ge(Li) spectrometer, and the study of ($d, p$) and ($d, t$) reactions utilizing 12-MeV deutrons and a broad range magnetic spectrograph. The observed levels are: the [523↓] ground-state rotational band, including the rotational states ${\frac{7}{2}}^{-}$, ${\frac{9}{2}}^{-}$, and $\frac{11}{2^{-}}$; the first 4 members of the [642↑] band, with the ${\frac{5}{2}}^{+}$ band head at 250.9 keV; the [521↓] band, including the members ${\mathrm{½}}^{-}$ (at 351.1 keV), ${\frac{3}{2}}^{-}$, ${\frac{5}{2}}^{-}$, and ${\frac{7}{2}}^{-}$; the lowest 4 members of the [521↑] band, with the ${\frac{3}{2}}^{-}$ state at 421.8 keV; the ${\mathrm{½}}^{+}$, ${\frac{3}{2}}^{+}$, and ${\frac{5}{2}}^{+}$ levels of a $K^{\pi }={\frac{1}{2}}^{+}$ band based at 737.6 keV, believed to be mainly a mixture of the vibrational configuration {[642↑], $K-2\mathrm{}$} and [660]; another $K^{\pi }={\frac{1}{2}}^{+}$ band based at 884.3 keV, including the ${\mathrm{½}}^{+}$, ${\frac{3}{2}}^{+}$, and ${\frac{5}{2}}^{+}$ states, assigned as mainly a three-quasiparticle configuration; a state at 820.8 keV, assigned as the head of a $K^{\pi }={\frac{3}{2}}^{-}$ band, probably of vibrational character; a state at 859.3 keV, assigned as the head of a $K^{\pi }={\frac{3}{2}}^{+}$ band; an $I^{\pi }={\frac{3}{2}}^{-}$ level at 1049.1 keV; and an $I^{\pi }={\frac{1}{2}}^{-}$ state at 1055.7 keV. In addition, the ${\frac{7}{2}}^{-}$ rotational level of the [512↑] band is probably at 799.5 keV, the ${\frac{3}{2}}^{-}$ state of the [510] band is indicated at 1200 keV, and a further state, probably of low spin, has been observed at 1058 keV. A number of other unassigned levels have been found in the ($d, p$), ($d, t$), and high-energy ($n, \gamma$) experiments. Essentially all states above 350 keV appear to be of mixed character, and several of the indicated "single-particle" bands are believed to have sizable vibrational components. Many of the $\gamma$-ray branching ratios among the three lowest negative-parity bands are anomalous, and the extent to which these deviations can be explained in terms of Coriolis coupling has been investigated.

• Received 6 September 1966

DOI:https://doi.org/10.1103/PhysRev.154.1146