Levels in ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ have been observed up to an excitation energy of 1900 keV using the ${}_{}{}^{171}{}_{}{}^{}\mathrm{Yb}$($t$,$\alpha$)${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ reaction. Many of the observed levels can be assigned as the successive coupling of the $\frac{1}{2^{+}}\left[411\mathrm{}\downarrow \right]$, $\frac{7}{2^{+}}\left[404\mathrm{}\downarrow \right]$, $\frac{5}{2^{+}}\left[402\mathrm{}\uparrow \right]$, $\frac{3}{2^{+}}\left[411\mathrm{}\uparrow \right]$, $\frac{7}{2^{-}}\left[523\mathrm{}\uparrow \right]$, and $\frac{5}{2^{+}}\left[413\mathrm{}\downarrow \right]$ protons to the $\frac{1}{2^{-}}\left[521\mathrm{}\downarrow \right]$ neutron. The following levels (denoted by bandhead energy in keV or energy of lowest spin member observed, spins assigned, $K^{\pi }$, and Nilsson configuration) have been assigned: 644, $I=4\mathrm{}$, $4^{-}$[404↓ + 521↓]; 716, $I=2\mathrm{}$, $2^{-}$[402↑ - 521↓]; $I=2\mathrm{}$ level at 744, $I=2\mathrm{} \mathrm{and} 3$, $1^{-}$[411↑ - 521↓]; 774, $I=3\mathrm{}$, $3^{-}$[404↓ - 521↓]; $I=5\mathrm{}$ level at 829, $I=5\mathrm{} \mathrm{and} 6$, $4^{+}$[523↑ + 521↓]; 851, $I=2\mathrm{} \mathrm{and} 3$, $2^{-}$[411↑ + 521↓]; 867, $I=3\mathrm{}$, $3^{-}$[402↑ + 521↓]; $I=5\mathrm{}$ level at 891, $I=5\mathrm{} \mathrm{and} 6$, $3^{+}$[523↑ - 521↓]; 1213, $I=3\mathrm{} \mathrm{and} 4$, $3^{-}$[413↓ + 521↓]; 1382, $I=2\mathrm{} \mathrm{to} 4$, $2^{-}$[413↓ - 521↓]. In addition, higher spin members of the [411↓ ± 521↓] ground state configuration and the $K^{\pi }=1^{-}$ $\gamma$-vibrational band built on the ground state have been proposed. Coriolis coupling calculations were performed, and anomalous experimental ($t$,$\alpha$) intensities were interpreted in terms of this interaction. Anomalous population of the previously known [411↓ ± 512↑] neutron excited state configuration has been observed and interpreted in terms of the residual neutron-proton interaction.

NUCLEAR REACTIONS ${}_{}{}^{171}{}_{}{}^{}\mathrm{Yb}$($t$,$\alpha$) ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ with isotopically enriched target; $E_t=17.0\mathrm{}$ MeV; measured $E_{\alpha }$ and $\sigma \left(\theta \right)$ with Q3D spectrometer; DWBA analysis; deduced levels $I^{\pi }$,$K$. NUCLEAR STRUCTURE ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ assigned Nilsson configurations; mixed bands $K^{\prime }$ of neutron excited state configuration with bands $K$ of proton excited state configuration satisfying condition ${\delta }_{K^{\prime },K}$.

• Received 9 February 1981

DOI:https://doi.org/10.1103/PhysRevC.24.1643