The shapes and collective behavior of rapidly rotating nuclei
Conference
·
OSTI ID:10160754
A review of our work on lifetime measurements of high-spin states in nuclei in the vicinity of neutron number 90 is presented. Recoil-distance experiments on {sup 159,160,161,162}Yb show a loss of collectivity for states having rotational frequencies in the range of {Dirac_h}{omega} {approximately} 0.26--0.36 MeV. In similar measurements on nuclei whose Fermi surfaces lie nearer to the middle of the i{sub 13/2} neutron shell ({sup 170, 171}W and {sup 172}Os), we have found no evidence for such losses in this frequency range. These patterns of behavior are in qualitative agreement with current cranking theories which predict an evolving triaxiality with positive {gamma} values for the nuclei very close to N = 90. In recent Doppler-broadened line shape measurements on {sup 160}Yb we found that in the frequency range of {Dirac_h}{omega} {approximately} 0.36--0.50 MeV there is a restoration of the collectivity to near that of the low-lying members of the ground band, a feature not predicted by cranking theories. Similar measurements on {sup 164}Yb show that the collectivity in the yrast sequence is fairly constant up to {Dirac_h}{omega}{approximately}0.42 MeV, with a loss showing up for states at somewhat higher frequencies. The trends of the transition quadrupole moments from available data on evenmass ytterbium nuclei with A = 160--168 are discussed and compared with theory.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10160754
- Report Number(s):
- CONF-9203162--2; ON: DE92017192
- Country of Publication:
- United States
- Language:
- English
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