LIMITS ON THE LIFETIME OF THE SHAPE ISOMER OF U-238

A theoretical calculation of the partial lifetime of the fission isomer in U-238 decaying via electric quadrupole radiation to the lowest 2+ state is presented and compared to experiment. This is a fully microscopic nuclear structure calculation using the constrained Hartree-Fock-Bogoliubov method, where the only input is the finite-ranged D1S interaction. The low-lying collective states are obtained via the Gaussian overlap approximation of the generator coordinate method. Rotational symmetry is restored within the rotor approximation. The computation of the transition rates provides an upper limit on the gamma-decay lifetime of the isomer, since only axial quadrupole deformations are considered.