The shapes and collective behavior of rapidly rotating nuclei
Conference
·
OSTI ID:7048275
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:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7048275
- Report Number(s):
- CONF-9203162-2; ON: DE92017192
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
663110* -- General & Average Properties of Nuclei & Nuclear Energy Levels-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
DEFORMATION
DOPPLER EFFECT
ENERGY LEVELS
FERMI LEVEL
HAMILTONIANS
HIGH SPIN STATES
ISOTOPES
LINE BROADENING
MATHEMATICAL OPERATORS
MOMENT OF INERTIA
NUCLEAR DEFORMATION
QUADRUPOLE MOMENTS
QUANTUM OPERATORS
RARE EARTH ISOTOPES
YTTERBIUM ISOTOPES
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
DEFORMATION
DOPPLER EFFECT
ENERGY LEVELS
FERMI LEVEL
HAMILTONIANS
HIGH SPIN STATES
ISOTOPES
LINE BROADENING
MATHEMATICAL OPERATORS
MOMENT OF INERTIA
NUCLEAR DEFORMATION
QUADRUPOLE MOMENTS
QUANTUM OPERATORS
RARE EARTH ISOTOPES
YTTERBIUM ISOTOPES