Energy Levels ofTm170

Twenty-seven levels in ${\mathrm{Tm}}^{170}$ have been observed up to an excitation energy of 1153 keV utilizing 12-MeV deuterons and the reaction ${\mathrm{Tm}}^{169}\mathrm{}(d,p)\mathrm{}{\mathrm{Tm}}^{170}$. The ground-state $Q$ value was determined as 4369±15 keV. Both magnetic Compton and germanium spectrometers have been used to measure 16 high-energy gamma rays up to an excitation energy of 868 keV resulting from the capture of thermal neutrons in the reaction ${\mathrm{Tm}}^{169}(n,\gamma ){\mathrm{Tm}}^{170}$. The neutron binding energy observed in this reaction is 6595±2.5 keV. In addition, 177 low-energy gamma rays between 38 and 870 keV have been observed in a bent-crystal spectrograph during irradiation of ${\mathrm{Tm}}^{169}$ with thermal neutrons. The multipolarities of 29 of the transitions were determined from internal conversion measurements with a beta-ray spectrometer. The analysis of these data suggests the existence of 23 levels up to an energy of 720 keV for which assignments have been attempted. Three Nilsson configurations 0, in which the proton orbital ${\Omega }_p$ remains $\frac{1}{2}+\left[411\mathrm{}\downarrow \right]$ and the neutron orbital ${\Omega }_n$ is successively $\frac{1}{2}-\left[521\mathrm{}\downarrow \right]$, $\frac{7}{2}+\left[633\mathrm{}\uparrow \right]$, and $\frac{5}{2}-\left[512\mathrm{}\uparrow \right] 0$, account for 16 states. This analysis leads to the following spectroscopic interpretation (band head energy, keV, in parentheses; spin, parity, and $K$ quantum number in brackets): (ground state), [1-, 1] with superimposed band to 4-; (149.721), [0-, 0] with superimposed band and anomalous spacings of even and odd spin members to 4-; (183.193), [3+, 3] with superimposed rotational members to 5+; (204.452), [2-, 2] with superimposed rotational members to 4-; (447.079), [3-, 3] only member of the band. Seven additional higher energy levels are tentatively assigned, five of which may arise from gamma vibrational bands at 411.45, 661.91, and 719.21 keV built on $K=1-$, $K=0-$ and $K=3+$ intrinsic bands, respectively. These are the first gamma vibrational bands postulated in odd-odd nuclei. All states below 425 keV from both ($d,p$) and direct high ($n,\gamma$) excitation are included in these assignments. The Coriolis coupling between the $K=1-$ and $K=0-$ bands is clearly observed in the anomalous rotational spacing of the $K=1-$ band. Calculation of the energies and ($d,p$) cross sections for the $K=1-$ and $K=0-$ bands agrees well with experiment and indicates that only the even members of these bands are appreciably mixed. The $M1\mathrm{}$ transition probabilities within the $K=0\mathrm{}$ rotational band in ${\mathrm{Tm}}^{170}$ are shown to be quite large. It is suggested that the high-energy gamma rays in the reaction ${\mathrm{Tm}}^{169}(n,\gamma ){\mathrm{Tm}}^{170}$ involve a direct reaction which excludes population of excited proton configurations.