Skyrme-QRPA calculations for low-lying excitation modes in deformed neutron-rich nuclei

TL;DR

This paper uses Skyrme-QRPA calculations to analyze low-lying excitation modes in deformed neutron-rich nuclei, revealing the microscopic structure and collective behavior of various vibrational modes near the neutron drip line.

Contribution

It systematically investigates the microscopic structure of low-frequency modes in neutron-rich magnesium isotopes using Skyrme-QRPA, highlighting the coupling mechanisms and evolution of vibrational modes near the drip line.

Findings

Strong collectivity in $^{34}$Mg and $^{40}$Mg due to coupling of $eta$ and pairing vibrations.

Gradual change in $K^{ extpi}=2^{+}$ modes linked to neutron Fermi level.

Proton particle-hole excitation influences $ ext{ extgamma}$-vibrations in near-drip-line nuclei.

Abstract

Low-frequency modes of excitation in deformed neutron-rich nuclei are studied by means of the quasiparticle random-phase approximation on the Skyrme-Hartree-Fock-Bogoliubov mean field. We investigate the microscopic structure of the soft $K^{\pi}=0^{+}$ modes systematically in neutron-rich Magnesium isotopes with $N=22, 24, 26$ and 28 close to the drip line, and it is found that the strong collectivity in $^{34}$Mg and $^{40}$Mg is acquired due to the coherent coupling between the $\beta$ vibration and the pairing vibration of neutrons. Microscopic structure of the $K^{\pi}=2^{+}$ modes changes gradually associated with the location of the Fermi level of neutrons, and it is found that the proton particle-hole excitation generating the $\gamma-$vibrational mode in $^{24}$Mg continues to play a key role in the near-drip-line nucleus $^{40}$Mg. The low-frequency octupole excitations are also investigated and the microscopic mechanism for the enhancement of transition strengths is discussed.