Nuclear Levels inLu177andLu175

Abstract

One- and three-quasiparticle states have been investigated in $^{175}\mathrm{Lu}$ and $^{177}\mathrm{Lu}$ using ($d,p$), ($d,t$), and thermal ($n,\ensuremath{\gamma}$) reactions on isotope-separated tarets of $^{176}\mathrm{Lu}$. The ($d,p$) and ($d,t$) studies utilized 12-MeV deuterons and a broad-range magnetic spectrograph; the ($n,\ensuremath{\gamma}$) studies used Ge(Li) and Si(Li) spectrometers. The ground-state one-quasiparticle band ${\frac{7}{2}}^{+}[404]$ through the ${\frac{17}{2}}^{+}$ member and four tentative three-quasiparticle bands are observed in $^{175}\mathrm{Lu}$. Members of the following one-quasiparticle bands are observed in $^{177}\mathrm{Lu}:{\frac{7}{2}}^{+}[404]$ ground state, ${\frac{9}{2}}^{\ensuremath{-}}[514]$, ${\frac{5}{2}}^{+}[402]$, and ${\mathrm{\textonehalf{}}}^{+}$[411]; in addition the following three-quasiparticle bands are observed in $^{177}\mathrm{Lu}:{\frac{23}{2}}^{\ensuremath{-}}[p404\ensuremath{\downarrow}+n514\ensuremath{\downarrow}+n624\ensuremath{\uparrow}]$, ${\frac{11}{2}}^{+}[p514\ensuremath{\uparrow}+n624\ensuremath{\uparrow}+n514\ensuremath{\downarrow}]$, ${\frac{13}{2}}^{+} \mathrm{and} {\frac{15}{2}}^{+}[p404\ensuremath{\downarrow}+n514\ensuremath{\downarrow}\ifmmode\pm\else\textpm\fi{}n510\ensuremath{\uparrow}]$, $K+2\ensuremath{\gamma}$ vibration built on the ${\frac{7}{2}}^{+}[404]$ ground state, tentatively ${\frac{17}{2}}^{+}[p404\ensuremath{\downarrow}+n514\ensuremath{\downarrow}+n512\ensuremath{\downarrow}]$, and tentatively ${\frac{13}{2}}^{+}$ and ${\frac{15}{2}}^{+}[p404\ensuremath{\downarrow}+n514\ensuremath{\downarrow}\ifmmode\pm\else\textpm\fi{}n521\ensuremath{\downarrow}]$. The neutron separation energy of $^{177}\mathrm{Lu}$ has been measured as 7072.7 \ifmmode\pm\else\textpm\fi{} 2.0 keV, and the $Q$ value for the reaction $^{176}\mathrm{Lu}(d,t)^{175}\mathrm{Lu}$ as -25\ifmmode\pm\else\textpm\fi{}15 keV. Identification of differential cross-section patterns to various members of three-quasiparticle rotational bands in both the ($d,p$) and ($d,t$) reactions indicates that this spectroscopic tool is also valuable for three-quasiparticle states. A sum rule is suggested and experimentally evaluated for the total differential cross sections in the ($d,p$) reaction to rotational members of the two different bands resulting from parallel and antiparallel coupling of the last neutron.