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Stabilization of nuclear isovector valence-shell excitations
G Rainovski1, N Pietralla, T Ahn
1Department of Physics and Astronomy, SUNY at Stony Brook, Stony Brook, New York 11794-3800, USA.
Physical Review Letters
|April 12, 2006
Summary
Researchers studied excited states in Cerium-138 (138Ce) using Coulomb excitation. They identified a mixed-symmetry state, finding its stability is linked to nuclear subshell structure.
Area of Science:
- Nuclear Physics
- Atomic Physics
Background:
- Understanding nuclear structure and the behavior of excited states is crucial in nuclear physics.
- Mixed-symmetry states offer insights into nuclear dynamics and collective excitations.
Purpose of the Study:
- To investigate the properties of excited states in Cerium-138 (138Ce) using Coulomb excitation.
- To identify and characterize mixed-symmetry states in 138Ce and their dependence on nuclear structure.
Main Methods:
- Utilized the 12C(138Ce, 138Ce*) Coulomb excitation reaction at 480 MeV.
- Measured relative cross sections via gamma-ray yields using the Gammasphere detector array.
- Analyzed E2 and M1 strength distributions for the lowest six 2+ states up to 2.7 MeV.
Main Results:
- Identified the 2(4)+ state in 138Ce as the primary component of the one-phonon mixed-symmetry state.
- Observed significant mixing between this mixed-symmetry state and a nearby isoscalar state.
- This mixing was found to be over four times larger than in the neighboring isotone, Barium-136 (136Ba).
Conclusions:
- The findings provide direct evidence that the stability of mixed-symmetry states is strongly influenced by the underlying nuclear subshell structure.
- The enhanced mixing in 138Ce compared to 136Ba highlights the role of specific nuclear configurations in stabilizing these states.
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