Neutron excitations and interactions above theN=80superdeformed closed shell: Superdeformation in144Eu

Abstract

Three superdeformed bands have been observed in the nucleus ${}^{144}$Eu with the GAMMASPHERE spectrometer in its early implementation phase. The reaction used was ${}^{122}$Sn${(}^{27}$Al,5${n)}^{144}$Eu at a beam energy of 142 MeV. All three bands are identified as single-neutron excitations with respect to ${}^{143}$Eu. One band is a confirmation of a previously suggested candidate. It is assigned as the yrast sequence based on the $\ensuremath{\pi}{6}^{1}\ensuremath{\nu}{7}^{1}$ configuration, and is believed to undergo an interaction with the $\ensuremath{\nu}$[514]9/2${}^{\ensuremath{-}}$ orbital. The other two bands are assigned as signature partners based on the $\ensuremath{\pi}{6}^{1}\ensuremath{\nu}{6\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}^{1}$ configuration, where $6\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}$ corresponds to a mixed [651]1/2${}^{+}$/ [642]5/2${}^{+}$ state. The partner that contains the $\ensuremath{\alpha}$=-1/2 signature component of the $6\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}$ orbital is identified from a band crossing that occurs in related bands in ${}^{145}$Gd and ${}^{146}$Gd. Alignment plots suggest that the interaction strength becomes stronger as the mass number increases.