Abstract
Background: Since the first experimental observation, two-nucleon radioactivity has gained renewed attention since the early 2000s. The system is the lightest two-proton ground-state emitter, while was recently proposed to be the first two-neutron ground-state emitter ever observed. A proper understanding of their properties and decay modes requires a reasonable description of the three-body continuum.
Purpose: Study the ground-state properties of and within a general three-body model and investigate their nucleon-nucleon correlations in the continuum.
Method: The pseudostate (PS) method in hyperspherical coordinates, using the analytical transformed harmonic oscillator (THO) basis for three-body systems, is used to construct the and ground-state wave functions. These resonances are approximated as a stable PS around the known two-nucleon separation energy. Effective core- potentials, constrained by the available experimental information on the binary subsystems and , are employed in the calculations.
Results: The ground state of is found to present a strong dineutron configuration, with the valence neutrons occupying mostly an state relative to the core. The results are consistent with previous -matrix calculations for the actual continuum. The case of shows a clear symmetry with respect to its mirror partner, the two-neutron halo : The diproton configuration is dominant, and the valence protons occupy an orbit.
Conclusions: The PS method is found to be a suitable tool in describing the properties of unbound ground states. For both and , the results are consistent with previous theoretical studies and confirm the dominant dinucleon configuration. This favors the picture of a correlated two-nucleon emission.
5 More- Received 9 January 2018
- Revised 23 February 2018
DOI:https://doi.org/10.1103/PhysRevC.97.034613
©2018 American Physical Society