Outstanding problems in the band structures of Sm152

Abstract

The recent data on $B(E2)$ values, deduced from the multi-Coulex excitation of the low spin states in the decay of $^{152}\mathrm{Sm}$, and other experimental findings in the last two decades are compared with the predictions from the microscopic dynamic pairing plus quadrupole model of Kumar and Baranger. The 1292.8 keV ${2}^{+}$ state is assigned to the ${{0}_{3}}^{+}$ band, and the $K=2$ assignment of the 1769 keV ${2}^{+}$ state is confirmed. The anomaly of the shape coexistence of the assumed spherical \ensuremath{\beta} band versus the deformed ground band is resolved. The values from the critical point symmetry X(5) support the collective character of the \ensuremath{\beta} band. The problem with the two-term interacting boson model Hamiltonian in predicting \ensuremath{\beta} and \ensuremath{\gamma} bands in $^{152}\mathrm{Sm}$ leads to interesting consequences. The collective features of the second excited ${K}^{\ensuremath{\pi}}=\phantom{\rule{0.16em}{0ex}}{{0}_{3}}^{+}$ band are preferred over the ``pairing isomer'' view. Also the multiphonon nature of the higher lying ${K}^{\ensuremath{\pi}}={{2}_{2}}^{+}\phantom{\rule{0.16em}{0ex}}\ensuremath{\beta}\ensuremath{\gamma}$ band and ${K}^{\ensuremath{\pi}}={4}^{+}$ band are illustrated vis-\`a-vis the new data and the nuclear structure theory.