Intruder configurations in the A=33 isobars: 33Mg and 33Al

Area of Science:

• Nuclear Physics
• Atomic Physics
• Quantum Mechanics

Background:

• The
• island of inversion
• is a region in nuclear chart where nuclei exhibit exotic properties due to intruder configurations.
• Previous studies suggested specific configurations for nuclei around N=20, but experimental data remains limited.

Purpose of the Study:

• Investigate the beta decay of Magnesium-33 (N=21) to understand nuclear structure.
• Determine the configuration of the lowest excited states in the daughter nucleus, Aluminum-33 (N=20).
• Clarify the parity of the ground state of Magnesium-33.

Main Methods:

• Experimental study of the beta decay of Magnesium-33.
• Analysis of decay branches and energy levels in Aluminum-33.
• Theoretical interpretation of nuclear configurations based on experimental observables.

Main Results:

• The lowest excited states in Aluminum-33 (N=20) exhibit a significant 2p-2h intruder configuration.
• This observation extends the known
• island of inversion
• beyond the Magnesium isotopes.
• The beta decay supports a positive parity for the Magnesium-33 ground state, contradicting prior g-factor measurements.

Conclusions:

• The study confirms the presence of intruder configurations in the N=20 daughter nucleus, Aluminum-33.
• The findings necessitate a revision of the nuclear shell structure models in this region.
• A mixed configuration (1p-1h and 3p-3h) is proposed for the Magnesium-33 ground state to reconcile experimental data.