Dipole excitation and geometry of borromean nuclei

TL;DR

This paper models the Coulomb breakup of borromean nuclei $^{11}$Li and $^{6}$He using a three-body approach to understand their dipole excitation and geometry, including neutron correlations and spatial configurations.

Contribution

It introduces a three-body model with density-dependent contact interaction to analyze Coulomb breakup and extract nuclear geometries without unphysical assumptions.

Findings

Reproduces B(E1) strength near threshold accurately.

Extracts core-neutron rms distances without sum rule limitations.

Finds mean opening angles consistent with model predictions.

Abstract

We analyze the Coulomb breakup cross sections of $^{11}$Li and $^6$He nuclei using a three-body model with a density-dependent contact interaction. We show that the concentration of the B(E1) strength near the threshold can be well reproduced with this model. With the help of the calculated B(E1) value, we extract the root-mean-square (rms) distance between the core nucleus and the center of mass of two valence neutrons without resorting to the sum rule, which may suffer from unphysical Pauli forbidden transitions. Together with the empirical rms distance between the neutrons obtained from the matter radius study and also from the three-body correlation study in the break-up reaction, we convert these rms distances to the mean opening angle between the valence neutrons from the core nucleus. We find that the obtained mean opening angles in $^{11}$Li and $^6$He agree with the three-body model predictions.