Microscopic description of large-amplitude shape-mixing dynamics with inertial functions derived in local quasiparticle random-phase approximation

TL;DR

This paper develops a microscopic method to describe large-amplitude shape-mixing dynamics in nuclei, accurately predicting excitation spectra and shape coexistence phenomena by incorporating inertial functions derived from local quasiparticle RPA.

Contribution

It introduces a new approach to derive inertial functions for the 5D quadrupole Hamiltonian using local normal modes on constrained HFB states, improving modeling of nuclear shape dynamics.

Findings

Increased vibrational and rotational masses due to time-odd mean-field components.

Excellent agreement with experimental excitation spectra and transition data.

Characterization of low-lying states as intermediate between shape coexistence and gamma instability.

Abstract

On the basis of the adiabatic self-consistent collective coordinate method, we develop an efficient microscopic method of deriving the five-dimensional quadrupole collective Hamiltonian and illustrate its usefulness by applying it to the oblate-prolate shape coexistence/mixing phenomena in proton-rich 68,70,72Se. In this method, the vibrational and rotational collective masses (inertial functions) are determined by local normal modes built on constrained Hartree-Fock-Bogoliubov states. Numerical calculations are carried out using the pairing-plus-quadrupole Hamiltonian including the quadrupole-pairing interaction. It is shown that the time-odd components of the moving mean-field significantly increase the vibrational and rotational collective masses in comparison with the Inglis-Belyaev cranking masses. Solving the collective Schroedinger equation, we evaluate excitation spectra, quadrupole transitions and moments. Results of the numerical calculation are in excellent agreement with recent experimental data and indicate that the low-lying states of these nuclei are characterized as an intermediate situation between the oblate-prolate shape coexistence and the so-called gamma unstable situation where large-amplitude triaxial-shape fluctuations play a dominant role.