Superdeformed band up to spin ∼(127/2 in ^{149}Gd

Abstract

A rotational band of nineteen transitions, extending to spin\ensuremath{\sim}(127/2\ensuremath{\Elzxh} and with an average moment of inertia ${\mathrm{scrI}}^{(2)}$ of 77 ${\ensuremath{\Elzxh}}^{2}$ ${\mathrm{MeV}}^{\mathrm{\ensuremath{-}}1}$, has been observed in $^{149}\mathrm{Gd}$. Its intensity accounts for approximately (1/2% of the total fusion cross section. Lifetime measurements yielded an average quadrupole moment of 17\ifmmode\pm\else\textpm\fi{}2 e-b, in excellent agreement with the value calculated microscopically for a superdeformed shape. The trends in ${\mathrm{scrI}}^{(1)}$ and ${\mathrm{scrI}}^{(2)}$ are consistent with very weak pairing effects. The data also suggest that to populate superdeformed bands significantly one must form cold residual nuclei.