Coupled-cluster calculation of the ^3-5He isotopes with Gamow-Hartree-Fock basis

We present ab-initio CCSD calculations of the ^3-5He ground states. We perform these calculations using a mixed basis of oscillator and complexWoods-Saxon states for chosen partial waves. From this starting point, we build a spherical Gamow-Hartree-Fock basis from a renormalized interaction of the low-momentum type generated from the N³LO two-body potential. The Gamow- Hartree-Fock basis, which is a Berggren basis, treats bound, resonant, and continuum states on an equal footing, and is therefore optimal for the description of nuclear states which may be embedded in the continuum. Within this ab-initio approach, we are able to calculate that ^3-4He are stable against particle decay, while ⁵He has a non-negligible width and is therefore unstable with respect to one neutron emission, as is the case experimentally. We illustrate from these calculations that the CCSD approach is as accurate for closed-shell nuclei as for open-shell nuclei with ±1 nucleon outside a closed-shell. Finally, we perform various tests on the convergence of our CCSD results. We find that our results are well converged with respect to basis size and discretization of the continuum integral defining our Berggren basis.