Single-particle and collective motion in unbound deformed Mg39

Abstract

Background: Deformed neutron-rich magnesium isotopes constitute a fascinating territory where the interplay between collective rotation and single-particle motion is strongly affected by the neutron continuum. The unbound f p-shell nucleus 39 Mg is an ideal candidate to study this interplay.Purpose: In this work, we predict the properties of low-lying resonant states of 39 Mg, using a suite of realistic theoretical approaches rooted in the open quantum system framework. − ground-state candidate exhibits a resonant structure reminiscent of that of its one-neutron halo neighbor 37 Mg, which is dominated by the f 7 2 partial wave at short distances and a p 3 2 component at large distances. A J Conclusion:We demonstrate that the subtle interplay between deformation, shell structure, and continuum coupling can result in a variety of excitations in an unbound nucleus just outside the neutron drip line.

Nonempirical Interactions for the Nuclear Shell Model: An Update

“…In valence-space configuration interaction calculations, one obtains what is colloquially known as the Gamow Shell Model (GSM), which entails the large-scale diagonalization of a complex symmetric Hamiltonian (278). Applications of this method to weakly bound nuclei have been quite successful (281)(282)(283)(284)(285)(286)(287)(288)(289), and there is a push to move from the commonly used phenomenological interactions to fundamental ones (289). The Berggren basis has been used successfully in ground-and excited-state CC calculations (see, e.g., (128,210)), hence the inclusion in VS-IMSRG and SMCC is technically straightforward.…”

Energy spectrum of neutron-rich helium isotopes: Complex made simple

“…The numerical resolution of the many-body problem is performed using the density matrix renormalization group (DMRG) method for open quantum systems [51,57] or Gamow-DMRG (G-DMRG), which has been shown to be a powerful technique to handle large many-body spaces. Also, working within a basis generated with natural orbitals [58] allows to significantly speed-up the numerical convergence of the G-DMRG method [59][60][61].…”

“…This is another difference with halo-EFT at leading-order as in the latter case the interaction is given by a regularized delta force in the 1 S 0 channel [42,43], which can be taken in a single Gaussian form. We stick to the original FHT form factor as it has proven to perform well in earlier studies [36,53,60,69]; our objective is to show how a simple, well established Hamiltonian based on effective scale arguments can capture the complex energy relations within the neutron-rich helium chain.…”

Two-neutron halo structure of F31

“…GSM is then the tool of choice to study manybody halo and resonance states. Following the success of former GSM applications [19][20][21][22], we will consider a model consisting of valence protons and neutrons interacting with a Furutani-Horiuchi-Tamagaki (FHT) interaction [28,29] above an 24 O core. The FHT interaction is a Gaussian-based residual interaction bearing central, spin-orbit and tensor terms, whose coupling constants are denoted as V ST c ,V ST LS and V ST T , respectively, where S = 0, 1 and T = 0, 1 are the spin and isospin of the two nucleons, respectively.…”