Swelling of nuclei embedded in neutron-gas and consequences for fusion

TL;DR

This paper investigates how neutron-gas environments affect the structure and fusion cross-sections of neutron-rich nuclei like Oxygen and Calcium, revealing increased swelling and fusion rates at high neutron densities relevant to neutron star crusts.

Contribution

It provides new insights into the impact of neutron-gas density on nuclear swelling and fusion cross-sections, especially near the neutron drip line in astrophysical contexts.

Findings

Neutron-gas density causes nuclei to swell and reach the drip-line.

Fusion cross-sections increase significantly at high neutron-gas densities.

Minimal fusion cross-section modification occurs at lower neutron-gas densities.

Abstract

Fusion of very neutron rich nuclei may be important to determine the composition and heating of the crust of accreting neutron stars. We present an exploratory study of the effect of the neutron-gas environment on the structure of nuclei and the consequences for pycnonuclear fusion cross-sections in the neutron drip region. We studied the formation and properties of Oxygen and Calcium isotopes embedded in varying neutron-gas densities. We observe that the formed isotope is the drip-line nucleus for the given effective interaction. Increasing the neutron-gas density leads to the swelling of the nuclear density. We have used these densities to study the effect of this swelling on the fusion cross-sections using the S\~{a}o-Paulo potential. At high neutron-gas densities the cross-section is substantially increased but at lower densities the modification is minimal.