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This work presents the first continuum shell-model study of weakly bound neutron-rich nuclei involving multiconfiguration mixing. For the single-particle basis, the complex-energy Berggren ensemble representing the bound single-particle states, narrow resonances, and the non-resonant continuum background is taken. Our shell-model Hamiltonian consists of a one-body finite potential and a zero-range residual two-body interaction. The systems with two valence neutrons are considered. The Gamow shell model, which is a straightforward extension of the traditional shell model, is shown to be an excellent tool for the microscopic description of weakly bound systems. It is demonstrated that the residual interaction coupling to the particle continuum is important; in some cases, it can give rise to the binding of a nucleus.

This work reviews foundations and applications of the complex-energy continuum shell model that provides a consistent many-body description of bound states, resonances, and scattering states. The model can be considered a quasi-stationary open quantum system extension of the standard configuration interaction approach for well-bound (closed) systems.

Recently, the shell model in the complex k-plane (the so-called Gamow Shell Model) has been formulated using a complex Berggren ensemble representing bound single-particle states, single-particle resonances, and non-resonant continuum states. In this framework, we shall discuss binding energies and energy spectra of neutron-rich helium and lithium isotopes. The single-particle basis used is that of the Hartree-Fock potential generated self-consistently by the finite-range residual interaction.

The shell model in the complex k-plane (the so-called Gamow Shell Model) has recently been formulated and applied to structure of weakly bound, neutron-rich nuclei. The completeness relations of Newton and Berggren, which apply to the neutron case, are strictly valid for finite-range potentials. However, for long-range potentials, such as the Coulomb potential for protons, for which the arguments based on the Mittag-Leffler theory do not hold, the completeness still needs to be demonstrated. This has been done in this paper, both analytically and numerically. The generalized Berggren relations are then used in the first Gamow Shell Model study of nuclei having both valence neutrons and protons, namely the lithium chain. The single-particle basis used is that of the Hartree-Fock-inspired potential generated by a finite-range residual interaction. The effect of isospin mixing in excited unbound states is discussed

We formulate the Gamow shell model (GSM) in coupled-channel (CC) representation for the description of proton/neutron radiative capture reactions and present the first application of this new formalism for the calculation of cross-sections in mirror reactions 7 Be(p, γ) 8 B and 7 Li(n, γ) 8 Li. The GSM-CC formalism is applied to a translationally-invariant Hamiltonian with an effective finiterange two-body interaction. Reactions channels are built by GSM wave functions for the ground state 3 2 − and the first excited state 1 2 − of 7 Be/ 7 Li and the proton/neutron wave function expanded in different partial waves.PACS numbers: 03.65. Nk, 33.15.Ry

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