Rotational and Intrinsic Levels inTm169andLu175

Abstract

Nuclear levels in ${\mathrm{Tm}}^{169}$ excited by electron capture of ${\mathrm{Yb}}^{169}$, and levels in ${\mathrm{Lu}}^{175}$ excited by both beta decay of ${\mathrm{Yb}}^{175}$ and electron capture of ${\mathrm{Hf}}^{175}$ have been studied by using the curved-crystal gamma-ray spectrometer and the ring-focusing beta-ray spectrometer, as well as a semicircular beta-ray spectrometer for low energies. From the precision energies and the multipolarity determinations, the levels in ${\mathrm{Tm}}^{169}$ have the following energies in kev, and spin and parity assignments: $A$ (ground state) (½+), $B8.42(\frac{3}{2}+)$, $C118.20(\frac{5}{2}+)$, $D138.95(\frac{7}{2}+)$, $E316.19(\frac{7}{2}+)$, $F379.31(\frac{7}{2}-)$, $G472.91(\frac{9}{2}-)$. Levels $A$, $B$, $C$, and $D$ are members of a rotational band whose characteristic constants are given. Levels $E$ and $F$ are interpreted as particle excitations and level $G$ as a rotational level based on the state $F$. The ${\mathrm{Lu}}^{175}$ excited states have the following energies in kev, spins, and parities: $A$ (ground state) ($\frac{7}{2}+$), $B 113.81 (\frac{9}{2}+)$, $C 251.46 (\frac{11}{2}+)$, $D 343.40 (\frac{5}{2}+)$, $E 396.31 (\frac{9}{2}-)$, $F 432.76 (\frac{7}{2}+)$, $G 504.7 (\frac{1}{2}+)$. $A$, $B$, and $C$ form a rotational band for which the characteristic constants are given. Some features of the levels and transition probabilities are discussed and compared with the unified model. A brief survey of second-order rotational energy constants and of intrinsic excitation levels is given.