Large enhancement of total reaction cross sections at the edge of the island of inversion in Ti, Cr, and Fe isotopes

TL;DR

This paper investigates the nuclear structure of neutron-rich Ti, Cr, and Fe isotopes near N=40, revealing significant deformation effects and proposing that reaction cross section measurements can identify the island of inversion's edge.

Contribution

It introduces a systematic method to analyze nuclear deformation using Skyrme Hartree-Fock calculations and links deformation features to measurable reaction cross sections.

Findings

Large quadrupole and hexadecapole deformations are induced by intruder orbit occupation.

Enhancement of total reaction cross sections signals the edge of the island of inversion.

Density profile changes near the surface are characteristic of the deformation effects.

Abstract

A systematic analysis of nuclear deformation is made for neutron-rich Ti, Cr, and Fe isotopes to explore the nuclear structure in the island of inversion near N = 40, where strong nuclear deformation is predicted. The nuclear ground states are obtained by the Skyrme Hartree-Fock method in three-dimensional coordinate space, which properly describes any nuclear shape. Three types of Skyrme interactions are employed to generate various deformed states in its isotopic chain. We find that in the island of inversion the occupation of highly elongated intruder orbits induces not only large quadrupole deformation but also large hexadecapole deformation. This appears as a sizable enhancement of the nuclear matter radius, showing the characteristic shell effect of the density profile near the nuclear surface. We show that the edge of the island of inversion, where the intruder orbit starts being occupied, can be determined by measuring the enhancement of the total reaction cross section at high incident energy. The possibility of constraining the hexadecapole deformation by a measurement of the total reaction cross sections is discussed.