Superdeformed band up to spin ∼(127/2 in Gd149

A rotational band of nineteen transitions, extending to spin∼(127/2ħ and with an average moment of inertia scrI(2) of 77 ħ2 MeV-1, has been observed in Gd149. Its intensity accounts for approximately (1/2% of the total fusion cross section. Lifetime measurements yielded an average quadrupole moment of 17±2 e-b, in excellent agreement with the value calculated microscopically for a superdeformed shape. The trends in scrI(1) and 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.