Spin-Dependent Triaxial Deformation in Neutron-Rich Mo Isotopes

The Eurogam-2 array has been used to study {gamma} rays emitted following the spontaneous fission of a {sup 248}Cm source. Analysis of Doppler-broadened line shapes corresponding to decays from excited rotational states in neutron-rich Sr, Zr, and Mo fission fragments has enabled the first measurements of state lifetimes in these nuclei at around {ital I}=10. The results are consistent with a predicted rotation-induced change in the triaxiality of the yrast states of the Mo isotopes that contrasts with the more stable behavior observed in the Zr and Sr nuclei. {copyright} {ital 1996 The American Physical Society.}