Population and decay of high-spin states in /sup 157-161/Yb: evolution of nuclear shapes as a function spin and neutron number
The population and decay of the entry states in /sup 157-161/Yb and /sup 155-158/Er from the reactions of 136- and 149-MeV /sup 20/Ne with /sup 144/Nd and /sup 146/Nd have been investigated with the Spin Spectrometer gated with a Ge detector. Statistical-model calculations reproduce the main features of the entry state populations. The entry lines, as a function of multiplicity, M/sub ..gamma../ show changes in slope at high M/sub ..gamma../ which are due to changes in the decay mode as a result of changes in nuclear structure. Energy spectra of the continuum ..gamma..-rays and angular distributions as a function of M/sub ..gamma../ show the onset of a dipole component localized at 650 +- 100 keV accompanied by an equally intense quadrupole component at twice the energy that continues to evolve to higher energies with increasing multiplicity. For /sup 157/ /sup 158/ /sup 159/ /sup 160/ /sup 161/Yb the dipole component appears at M/sub ..gamma../ = 21,22,23,25, and 27 (at spin I approx. = 38,40,42,45, and 50), respectively. At precisely these multiplicities the entry lines show a decrease in slope. In /sup 158/Yb the dipole component disappears at M/sub ..gamma../ = 28 and the entry line resumes its original slope. The results are consistent with the following picture. At low spins for /sup 157/ /sup 158/Yb the nuclear shapes evolve from prolate to slightly oblate particle-aligned structures. At I approx. = 38,40,42,45, and 50 the /sup 157/ /sup 158/ /sup 159/ /sup 160/ /sup 161/Yb nuclei, respectively, develop high-K rotational bands which may be built on oblate structures with large deformation (epsilon approx. = 0.3). At I = 49 a transition to triaxial shape appears to occur in /sup 158/Yb.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Washington Univ., St. Louis, MO (USA). Dept. of Chemistry
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5101118
- Report Number(s):
- CONF-820738-1; ON: DE82018159
- Resource Relation:
- Conference: INS symposium on dynamics of nuclear collective motion, Mount Fuji, Japan, 6 Jul 1982
- Country of Publication:
- United States
- Language:
- English
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Evolution of nuclear shapes in /sup 157/-/sup 161/Yb as a function of spin and neutron number
Evidence for a transition from prolate to oblate to triaxial shapes in /sup 158/Yb
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HIGH SPIN STATES
MULTIPOLE TRANSITIONS
YTTERBIUM 158
YTTERBIUM 159
YTTERBIUM 160
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ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
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ROTATIONAL STATES
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ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY RANGE
EVEN-EVEN NUCLEI
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HEAVY ION REACTIONS
INFORMATION
INTERMEDIATE MASS NUCLEI
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MINUTES LIVING RADIOISOTOPES
NUCLEAR REACTIONS
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PARTICLE PROPERTIES
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651823* - Nuclear Properties & Reactions
A=150-189
Experimental- Energy Levels & Transitions- (-1987)