Gamow shell-model calculations of drip-line oxygen isotopes

TL;DR

This paper uses the Gamow shell model with a complex basis to accurately describe low-lying states and stability of drip-line oxygen isotopes, emphasizing the importance of continuum states and many-body correlations.

Contribution

It introduces a detailed GSM approach with a Berggren basis for oxygen isotopes, highlighting the role of continuum states and NN interaction components in nuclear stability.

Findings

Berggren basis is essential for describing unbound states.

Proper many-body correlations are crucial for binding energy predictions.

Loosely bound isotopes are influenced by the 1S0 NN interaction component.

Abstract

We employ the Gamow shell model (GSM) to describe low-lying states of the oxygen isotopes 24O and 25O. The many-body Schrodinger equation is solved starting from a two-body Hamiltonian defined by a renormalized low-momentum nucleon-nucleon (NN) interaction, and a spherical Berggren basis. The Berggren basis treats bound, resonant, and continuum states on an equal footing, and is therefore an appropriate representation of loosely bound and unbound nuclear states near threshold. We show that such a basis is necessary in order to obtain a detailed and correct description of the low-lying 1+ and 2+ excited states in 24O. On the other hand, we find that a correct description of binding energy systematics of the ground states is driven by proper treatment and inclusion of many-body correlation effects. This is supported by the fact that we get 25O unstable with respect to 24O in both oscillator and Berggren representations starting from a 22O core. Furthermore, we show that the structure of these loosely bound or unbound isotopes are strongly influenced by the 1S0 component of the NN interaction. This has important consequences for our understanding of nuclear stability.