Nuclear collectivity at high spins determined from lifetime measurements

Doppler-shift recoil-distance lifetime measurements have been performed on several nuclei whose Fermi surfaces ranged from the bottom to the middle of the i/sub 13/2/ neutron shell. The collective behavior deduced from the data is interpreted in terms of evolving triaxiality at high rotational frequencies as a result of the shape-driving influence of i/sub 13/2/ quasineutrons, in general agreement with both cranked shell model and self-consistent theories. Evidence is also presented for influence from h/sub 9/2/ protons at very low rotational frequencies in light tungsten nuclei. 21 refs., 8 figs