Collapse of Nuclear Collectivity along the N=Z Line

Area of Science:

• Nuclear Physics
• Atomic Physics
• Quantum Mechanics

Background:

• The N=Z nuclei region around A∼80 exhibits highly deformed shapes and strong collectivity.
• Understanding nuclear structure evolution in this region is crucial for nuclear models.

Purpose of the Study:

• To measure the lifetime of the J^{π}=2^{+} state in the self-conjugate ^{88}Ru nucleus.
• To investigate the quadrupole collectivity and nuclear deformation in this heavy N=Z nucleus.
• To compare experimental results with theoretical calculations.

Main Methods:

• Experiment utilizing rare-isotope beams from the Facility for Rare Isotope Beams.
• Population of ^{88}Ru via one-neutron knockout and charge-exchange reactions.
• Lifetime measurement using the triple-foil plunger technique.

Main Results:

• The lifetime of the J^{π}=2^{+} state in ^{88}Ru was determined to be 14.3_{-3.4}^{+2.5} ps.
• A significant drop in quadrupole collectivity was observed compared to lighter N=Z nuclei.
• Theoretical calculations suggest moderate triaxial deformation.

Conclusions:

• ^{88}Ru represents a transition towards less deformed shapes compared to the lighter N=Z region.
• Low-lying states in ^{88}Ru are not dominated by strong many-particle many-hole excitations.
• Experimental data provides a benchmark for nuclear structure theories in this mass region.