Shape coexistence in transitional nuclei in the A @ 120 mass region
High-spin states in the odd-proton nuclei {sup 119,121,123}I and {sup 121,127,131}Cs are studied following heavy-ion fusion-evaporation reactions using beams provided by the Stony Brook Tandem-LINAC accelerator. Gamma-rays resulting from deexcitations of high-spin states are measured using an array of six Compon-suppressed germanium detectors. Experiments performed include excitation functions, angular distributions, {gamma}-{gamma} coincidence and pulsed-beam E{sub {gamma}}-t measurements. Following theoretical predictions of competing prolate and oblate potential-energy minima, experimental evidence is presented for the coexistence of prolate and oblate nuclear shapes in {sup 119,121,123}I. Both prolate and oblate rotational bands are observed with the same single-quasiproton configuration in each nucleus. Rotational bands in the Z = 55 Cs isotopes are found to be prolate at low spins. At higher spins, these nuclei possesses different shapes ranging from prolate to oblate, depending on the neutron number N. These shape differences result from the alignment of an h{sub 11/2} neutron pair. The systematic behavior of neutron alignment is investigated. The change in the signature splitting and B(M1)/b(E2) ratios for bands below and above the alignment indicates that the shape changes are consistent with the {gamma}-driving properties of h{sub 11/2} neutrons. Finally, non-collective states are observed to become yrast at moderate spins in {sup 119}I and {sup 121}I.
- Research Organization:
- State Univ. of New York, Stony Brook, NY (United States)
- OSTI ID:
- 5260192
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
663560 -- Nuclear Mass Ranges-- A=90-149-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACCELERATORS
ALKALI METAL ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CESIUM 121
CESIUM 127
CESIUM 131
CESIUM ISOTOPES
DAYS LIVING RADIOISOTOPES
DE-EXCITATION
ELECTROMAGNETIC RADIATION
ELECTRON CAPTURE RADIOISOTOPES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EVAPORATION MODEL
GAMMA RADIATION
GE SEMICONDUCTOR DETECTORS
HEAVY ION FUSION REACTIONS
HIGH SPIN STATES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
IODINE 119
IODINE 121
IODINE 123
IODINE ISOTOPES
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LINEAR ACCELERATORS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MICROSEC LIVING RADIOISOTOPES
MINUTES LIVING RADIOISOTOPES
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEI
ODD-EVEN NUCL
ODD-EVEN NUCLEI
RADIATION DETECTORS
RADIATIONS
RADIOISOTOPES
SEMICONDUCTOR DETECTORS
SHAPE