Decay ofTm172

The decay of ${}_{69}{}^{172}{}_{}{}^{}\mathrm{Tm}$ to ${}_{70}{}^{172}{}_{}{}^{}\mathrm{Yb}$ has been studied with lithium-drifted germanium detectors used to obtain singles and coincidence spectra. A multiparameter analyzer was used for coincidence measurements. The measurements indicate the presence of 49 $\gamma$-ray transitions for which energies and intensities were obtained. The level scheme proposed for ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}$ has states with energies, spins, and parities of 0.0($0^{+}$), 78.70($2^{+}$), 260.2($4^{+}$), 1043($0^{+}$), 1119($2^{+}$), 1172.3($3^{+}$), 1262.9($4^{+}$), 1375.8($5^{+}$), 1466.0($2^{+}$), 1476.8($1^{-}$), 1549.2($3^{+}$), 1608.6($2^{+}$), 1662.6($3^{+}$), 1700.6($3^{+}$), 1750.0($4^{+}$), and 1806($4^{+}$) keV. The states at 1043 and 1119 keV form a $K^{\pi }=0^{+}$ rotational band of which the most likely interpretation is a pairing vibration. The data concerning the levels at 1172.3, 1262.9, and 1375.8 keV are consistent with their previous interpretation as members of a $K^{\pi }=3^{+}$ rotational band. A $K^{\pi }=2^{+}$ band with levels at 1466.0 and 1549.2 keV is interpreted as being, at least predominantly, a $\gamma$-vibrational band. It is suggested that the 1476.8-keV level may be a $K^{\pi }=0^{-}$ octupole vibrational state. The level at 1608.6 keV is interpreted as a two-neutron state with $K^{\pi }=2^{+}$ and with possible rotational levels at 1700.6 and 1806 keV.