The concept of spontaneous symmetry breaking is applied to the rotating mean field of nuclei. The description is based on the tilted-axis cranking model, which takes into account that the rotational axis can take any orientation with respect to the deformed density distribution. The appearance of rotational bands in nuclei is analyzed, focusing on weakly deformed nuclei at high angular momentum. The quantization of the angular momentum of the valence nucleons leads to new phenomena. Magnetic rotation represents the quantized rotation of the anisotropic current distribution in a near spherical nucleus. The restricted amount of angular momentum of the valence particles causes band termination. The discrete symmetries of the mean-field Hamiltonian provide a classification scheme of rotational bands. New symmetries result from the combination of the spatial symmetries of the density distribution with the vector of the angular momentum. The author discusses in detail which symmetries appear for a reflection-symmetric density distribution and how they show up in the properties of the rotational bands. In particular, the consequences of rotation about a nonprincipal axis and of breaking the chiral symmetry are analyzed. Also discussed are which symmetries and band structures appear for non-reflection-symmetric mean fields. The consequences of breaking the symmetry with respect to gauge and isospin rotations are sketched. Some analogies outside nuclear physics are mentioned. The application of symmetry-restoring methods to states with large angular momentum is reviewed.

Spontaneous symmetry breaking in rotating nuclei

Development and applications of the IGISOL technique

New insights from studies of spontaneous fission with large detector arrays

Nuclear Data Sheets for A=132

The O(6) → rotor transition in the PtOs nuclei

Levels in 110Pd, 112Pd, 114Pd and 116Pd from the beta decays of the on-line mass separated Rh isotopes

Lifetimes of yrast states in 110Cd

High-spin bands in 122,123,124Xe and 123Cs were populated using 3He- and 16, 18O-induced reactions on Te, Pd and Ag targets. The subsequent de-excitation was studied using gamma -ray and conversion-electron spectroscopic methods. States with spins up to Jpi =(25-), (35/2-), (21-) and (51/2-), respectively, were identified. In 122Xe four Delta I=2 bands were identified in addition to the ground state and gamma bands, and furthermore a Delta J=1 band with a tentative (K,I)pi =(10, 10)- band head was observed. In 123Xe the previously observed 11/2- and 7/2+ bands were extended to Jpi =(35/-) and (23/2+), respectively. The yrast cascade in 123Cs was extended to spin 51/2-. In 124Xe the recently presented level scheme was completed with some high-lying levels. The band structures were interpreted within the cranked shell model (CSM) framework. A consistent description of band crossing frequencies in both odd and even nuclides was obtained, and configurations were assigned to most of the observed bands. Some relative transition rates were obtained from branching intensities.

Neutron and proton bands in 122Xe at high spins

Excited states of $^{132}\mathrm{Ba}$ were studied in an experiment utilizing the $^{124}\mathrm{Sn}$${(}^{13}$C,5n) reaction at a beam energy of 65.5 MeV. The level scheme of $^{132}\mathrm{Ba}$ was considerably extended from what was previously known. Evidence is presented for neutron ${\mathit{h}}_{11/2}$ alignments, which are predicted to drive the nucleus to a shape with \ensuremath{\gamma}\ensuremath{\approxeq}-80\ifmmode^\circ\else\textdegree\fi{}. Two strongly coupled \ensuremath{\Delta}I=1 bands were also observed.

A. Pakkanen

Papers

Levels in 110Pd, 112Pd, 114Pd and 116Pd from the beta decays of the on-line mass separated Rh isotopes

Lifetimes of yrast states in 110Cd

Neutron and proton bands in 122Xe at high spins

Band structures in Ba 132

High-j bands in 173Ir