Shell Erosion and Shape Coexistence in (16)43S27.

Area of Science:

• Nuclear Physics
• Atomic Physics
• Quantum Mechanics

Background:

• The N=28 shell closure is a key feature in atomic nuclei.
• Its stability in neutron-rich isotopes is crucial for understanding nuclear structure.
• Evidence suggests this closure may collapse in certain neutron-rich nuclei.

Purpose of the Study:

• To measure the g-factor of the first isomeric state in Sulfur-43.
• To experimentally establish the spin-parity of this isomer.
• To provide direct evidence for the collapse of the N=28 shell closure.

Main Methods:

• g-factor measurement using advanced spectroscopic techniques.
• Analysis of isomeric decay properties (excitation energy and half-life).
• Comparison with theoretical nuclear models (shell model, beyond mean-field).

Main Results:

• The g-factor of the first isomeric state in Sulfur-43 was measured to be 0.317(4).
• The spin-parity of the isomer was determined to be 7/2-.
• The intruder nature of the ground state was confirmed, indicating shell structure changes.

Conclusions:

• The results provide unambiguous evidence for the collapse of the N=28 shell closure in neutron-rich nuclei.
• Nuclear shell model calculations consistently describe the coexistence of deformed prolate and quasispherical states in Sulfur-43 at low energies.