The isovector dipole strength in nuclei with extreme neutron excess

TL;DR

This paper systematically analyzes the E1 strength in very neutron-rich Sn nuclei using the Relativistic Quasiparticle Random Phase Approximation, revealing how neutron excess and deformation influence low-lying strength.

Contribution

It provides the first systematic study of E1 strength in extremely neutron-rich Sn isotopes, highlighting the effects of deformation and isospin asymmetry.

Findings

Deformation appears in nuclei beyond $^{142}$Sn due to neutron excess.

Neutron excess increases total low-lying E1 strength.

Deformation spreads and hinders low-lying strength, affecting experimental prospects.

Abstract

The E1 strength is systematically analyzed in very neutron-rich Sn nuclei, beyond $^{132}$Sn until $^{166}$Sn, within the Relativistic Quasiparticle Random Phase Approximation. The great neutron excess favors the appearance of a deformed ground state for $^{142-162}$Sn. The evolution of the low-lying strength in deformed nuclei is determined by the interplay of two factors, isospin asymmetry and deformation: while greater neutron excess increases the total low-lying strength, deformation hinders and spreads it. Very neutron rich deformed nuclei may not be as good candidates as stable spherical nuclei like $^{132}$Sn for the experimental study of low-lying E1 strength.