Mass, Spectroscopy, and Two-Neutron Decay of ^{16}Be

Area of Science:

• Nuclear Physics
• Exotic Nuclei Research

Background:

• Investigating the structure of neutron-rich isotopes like 16Be is crucial for understanding nuclear forces.
• Previous measurements of 16Be were limited, necessitating further study.

Purpose of the Study:

• To investigate the structure and decay properties of the most neutron-rich beryllium isotope, 16Be.
• To characterize newly observed resonances in 16Be and their decay modes.

Main Methods:

• Proton knockout reactions from a 17B beam.
• Analysis of decay products to identify resonance energies and widths.
• Theoretical calculations modeling three-body decay processes.

Main Results:

• Two new resonances were observed in 16Be at 0.84(3) MeV and 2.15(5) MeV above the two-neutron decay threshold.
• These resonances correspond to the ground (0+) and first excited (2+) states, with an excitation energy of 1.31(6) MeV.
• The mass excess of 16Be was determined to be 56.93(13) MeV, indicating it is more bound than previously measured.
• Both states decay via direct two-neutron emission.

Conclusions:

• The study provides the first observation of two new states in 16Be and their decay characteristics.
• Calculations support the presence of a compact dineutron component in the ground state of 16Be.
• The 2+ excited state exhibits a more diffuse neutron-neutron distribution, offering insights into nuclear correlations.