Dipole response of deformed halo nuclei $^{31}$Ne and $^{37}$Mg

TL;DR

This study investigates the electric dipole response of deformed halo nuclei $^{31}$Ne and $^{37}$Mg, revealing how neutron configurations and deformations significantly influence the soft dipole strength, with implications for experimental verification.

Contribution

It provides a detailed analysis of the configuration dependence of the $E1$ strength in deformed halo nuclei using a deformed Woods-Saxon potential, highlighting the impact of specific neutron orbit configurations.

Findings

Halo configurations greatly enhance threshold $E1$ strength.

$^{37}$Mg shows about 60 ext% larger soft dipole strength than $^{31}$Ne.

Deformation and neutron orbit configurations are crucial for understanding dipole responses.

Abstract

We study the soft electric dipole ($E1$) response of deformed halo nuclei $^{31}$Ne and $^{37}$Mg using a deformed Woods-Saxon potential, with the potential depth adjusted to reproduce empirical separation energy of last neutron orbit, i.e., 150 keV for $^{31}$Ne and 220 keV for $^{37}$Mg. The configuration dependence of the $E1$ strength near the neutron threshold is pointed out. The halo configurations $[321]3/2$ at $\beta_2=0.5$ and $[330]1/2$ at $\beta_2=0.24$ in $^{31}$Ne contain large amplitudes of halo $p$-shell orbits, which significantly enhance the threshold strength by several times compared to the non-halo configuration $[202]5/2$ at $\beta_2=0.32$. In $^{37}$Mg, the last neutron configuration is assigned as $[321]1/2$ at a large deformation of $\beta_2=0.46$, which involves a halo $p$-shell configuration that significantly enhances the soft dipole strength. This enhancement is about 60\% larger than that of the $[321]3/2$ configuration in $^{31}$Ne because of large $p$-shell probability in $^{37}$Mg. Experimental confirmation of the soft dipole strength is highly desired to determine the deformation and the configuration of the last neutron orbits both in $^{31}$Ne and $^{37}$Mg.