N = 16 spherical shell closure in 24O

Area of Science:

• Nuclear Physics
• Atomic and Molecular Physics

Background:

• Investigating the properties of exotic nuclei near the neutron drip-line is crucial for understanding nuclear structure and stability.
• The N=16 shell closure is a significant feature in nuclear physics, influencing the stability and behavior of isotopes.

Purpose of the Study:

• To investigate the unbound excited states of the neutron drip-line isotope oxygen-24 (24O).
• To determine the spin parity and quadrupole transition parameter of the first excited state in 24O.
• To provide experimental evidence for the N=16 shell closure in 24O.

Main Methods:

• Utilized the 24O(p,p')23O + n reaction in inverse kinematics.
• Employed a beam energy of 62 MeV/nucleon.
• Reconstructed the decay energy spectrum of 24O* from the momenta of 23O and the neutron.

Main Results:

• Identified the first excited state in 24O at an excitation energy of E(x) = 4.65 ± 0.14 MeV.
• Determined the spin parity of this state to be J(π) = 2+.
• Deduced the quadrupole transition parameter β2 for the 2(1)+ state as 0.15 ± 0.04.

Conclusions:

• The observed high excitation energy and small β2 value support the presence of the N=16 shell closure in 24O.
• These findings contribute to the understanding of nuclear shell structure in neutron-rich isotopes.
• The study provides valuable data for nuclear models aiming to describe exotic nuclei.