Thursday 8 March 2018, 1.00PM
Speaker(s): Dr. Jagjit Singh Dhinds
In the recent years, there has been rapidly increasing interest in the study of the 2n- halo nuclei sitting right on the top of neutron driplines and 2n- decays of the unbound systems beyond the neutron dripline. These systems demands a three-body description with proper treatment of con- tinuum, the conventional shell-model assumptions being insufficient. Recently we have developed a 3 - body (core+n + n) structure model for ground and continuum states of the 2n- halo nuclei [1, 2]. Initially it is implemented for 6He. Very recently a high precision measurement of interaction cross-section for 22C was made on a carbon target at 235 MeV/nucleon  and also the unbound nucleus 26O has been investigated, using invariant-mass spectroscopy  at RIKEN Radioactive Isotope Beam Factory. These high precision measurements, are the motivation for extending our past study to the 2n-halo 22C and 2n- unbound system 26O.
I will present the ground state properties of 6He, 22C and 26O systems and transitions to the continuum that might be of help in disentangling the still poorly known low-energy resonances and predicting new resonances of these nuclei. We compare our findings with the more recent experimental works and the scarce theoretical work that has been done in the recent past on these systems.
The neutron single-particle unbound spdf- continuum states of the sub-systems (core+n) are calculated in a simple shell model picture for different continuum energy cut-off’s by using a Dirac delta normalization and are checked with a more refined phase-shift analysis. The sensitivity of the (core+n) potential has been explored for the emergence of different dominant configurations in the ground state of 6He, 22C and 26O. These (core+n) continuum wavefunctions are used to construct the two-particle states by proper angular momentum couplings and taking contribution from different configurations. The role of different pairing interactions such as density independent (DI) contact-delta pairing interaction and density dependent (DD) contact-delta pairing interaction in the structure of these systems has been explored. Our calculations shows how the ground state displays a collective nature, taking contribution from many different oscillating continuum states that coherently sum up to give an exponentially decaying bound wavefunction in 6He, 22C and an oscillating unbound wavefunction in case of 26O.