Structure of neutron-rich carbon isotopes: shell evolution and two-neutron-halo at the dripline

Structure of neutron-rich carbon isotopes are studied by shell-model with new shell-model Hamiltonians, SFO-tls [1] and YSOX [2], as well as microscopic G-matrix including an extended version [3] with contributions from three-nucleon forces. Evolution of effective single-particle energies and ground-state energies is discussed with emphasis on the roles of tensor and three-nucleon forces. Proton shell gap energies of the isotopes support the new magicity at $Z$=6 [4].

Structure and formation of two-neutron halo at the dripline nucleus $^{22}$C are studied by a three-body model with the use of low-energy limit of neutron-neutron interaction [5]. Relation between two-neutron separation energy and halo radius is derived assuming a correlated $^{20}$C-core with appreciable 2s$_{1/2}$-shell admixtures.

The three-body model is extended to the case of mixed configurations of 2s$_{1/2}^2$ + 1d$_{5/2}^2$, and applied to $^{17}$B.

 

[1] T. Suzuki and T. Otsuka, Phys. Rev. C 78, 061302 (2008).

[2] C. Yuan et al., Phys. Rev. C 85, 064324 (2012).

[3] M. Hjorth-Jensen et al, Phys. Rep. 261, 125 (1995);

N. Tsunoda et al., Phys. Rev. C 95, 021304 (R) (2017).

[4] D. T. Tran et al., Nature Communications 9, 1594 (2017).

[5] T. Suzuki and T. Otsuka, Physics Letters B 753, 199 (2016).