Beyond the Unified Model

TL;DR

This paper critically examines the Unified Model of nuclear structure, comparing its assumptions with experimental data, and introduces microscopic derivations and concepts like spontaneous symmetry breaking to explain complex rotational phenomena.

Contribution

It provides a microscopic derivation of the Bohr Hamiltonian and refines the understanding of rotational degrees of freedom using spontaneous symmetry breaking.

Findings

Separation of collective and intrinsic degrees becomes invalid after 5-10 collective quanta.

Microscopic derivation of the Bohr Hamiltonian aligns with experimental data.

Descriptions of phenomena like tilted-axis rotation and band termination are improved.

Abstract

The key elements of the Unified Model are reviewed and checked against modern experimental data. For medium-mass or heavy nuclei it is found that separation between collective and intrinsic degrees freedom becomes invalid for after exciting five to ten collective quanta along the yrast line and two quanta above it. The microscopic derivation of the Bohr Hamiltonian by means of adiabatic time-dependent mean field theory is presented and results compared with experiment. The description of the strong coupling between the rotational and intrinsic degrees of freedom in framework of the rotating mean field is described from a conceptual point of view. The classification of rotational bands as configurations of rotating quasiparticles is introduced. Using the concept of spontaneous symmetry breaking the microscopic underpinning of the rotational degrees is refined. Resulting phenomena, as tilted-axis rotation, transverse wobbling, chirality, magnetic rotation, and band termination are discussed.