Effects of the shape and Coriolis interaction in nuclear electromagnetic properties

Nikolay Minkov,N Arsenyev,A Bezbakh,T Shneidman,A Vdovin,I Rogov

doi:10.1051/epjconf/201819401005

Abstract

We study the manifestation of collective vibrations and rotations coupled to single-particle motion in odd-mass nuclei with the presence of axial quadrupole-octupole deformations. Our model incorporates K-mixing effects stemming from the Coriolis interaction between the odd nucleon and the even-even core and thus takes into account the probabilities for otherwise forbidden due to the axial symmetry electromagnetic transitions between excited states built on different intrinsic configurations. We demonstrate these effects in the quasi-parity-doublet spectrum of the nucleus 221Fr in which a strong Coriolis interaction manifests. The model successfully describes the available intra- and interband E1, E2 and M1 transition rates giving an insight into the mechanism which allows the K-suppressed transitions in axially symmetric nuclei.

Highlights

The role of the shape deformations in the manifestation of variety of dynamical effects in the structure of nuclear energy spectra and electromagnetic transitions is one of the continuously challenging problems in the theoretical and experimental nuclear structure study [1]
The problem becomes even more challenging when referred to the interplay between collective and intrinsic degrees of freedom especially important in odd mass nuclei. This has been the subject of a model development involving the consideration of quadrupole-octupole vibration-rotation motion in the even-even core [3,4,5,6], the motion of the odd nucleon within a reflection-asymmetric axially-deformed potential [7] with pairing correlations of Bardeen–Cooper–Schrieffer (BCS) type implemented as in Ref. [8], and the Coriolis interaction between the core and the nucleon taken into account through the perturbation theory in a fully microscopic way [9]
In the present work we examine the aforementioned K-mixing formalism in the case of a much stronger Coriolis interaction observed in the QPD spectrum of 221Fr

Summary

Introduction

The role of the shape deformations in the manifestation of variety of dynamical effects in the structure of nuclear energy spectra and electromagnetic transitions is one of the continuously challenging problems in the theoretical and experimental nuclear structure study [1]. The problem becomes even more challenging when referred to the interplay between collective and intrinsic degrees of freedom especially important in odd mass nuclei This has been the subject of a model development involving the consideration of quadrupole-octupole vibration-rotation motion in the even-even core [3,4,5,6], the motion of the odd nucleon within a reflection-asymmetric axially-deformed potential [7] with pairing correlations of Bardeen–Cooper–Schrieffer (BCS) type implemented as in Ref. It has been shown that within this formalism the spectra of oddmass nuclei with quadrupole-octupole degrees of freedom can be described in terms of yrast and non-yrast quasiparity-doublets (QPDs) — quadrupole-octupole vibrationrotation modes — built on one-quasiparticle excitations (bandheads) mixed though the Coriolis coupling [9] It was demonstrated for the QPD energy levels of 223Ra and 221Fr that the model is capable to take into account both the Coriolis decoupling and K-mixing effects.

Model of quadrupole-octupole core plus particle

C C δ Iπ

K f N I2i πi

QPD spectrum and transition rates with strong Coriolis interaction in 221Fr

Concluding remarks