Decreasing Collectivity in Smoothly Terminating Bands in the A ∼ 110 Region

Lifetimes of states in two rotational bands in {sup 108}Sn and one in {sup 109}Sb have been determined using the Doppler shift attenuation method. The deduced quadrupole moments for the states are in excellent agreement with cranked Nilsson model predictions, which imply a gradual change in the nuclear shape from collective near-prolate at medium spin to noncollective oblate at high spin. This change results from the gradual alignment of the spin vectors of the valence particles and holes in a specific configuration. These data provide crucial evidence in support of the phenomenon of smooth band termination. {copyright} {ital 1998} {ital The American Physical Society}