Coexistence in even-mass nuclei

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

https://www.hzdr.de/publications/000736/736.pdf

Tilted rotation of triaxial nuclei

Quadrupole pairing interaction and signature inversion

Candidate chiral band in 134 La

Interplay between proton and neutron S-bands in the Xe-Ba-Ce-region

Lifetime measurements of high spin states in Yb nuclei

High spin states of128Ba have been investigated via the96Zr (36S, 4n)reaction at 150Me V beam energy using the Osiris anti- compton spectrometer. 14new levels and 23new transitions up to a maximum spin of 34ħ could be placed in the levelscheme.

K. Schiffer

Papers

Interplay between proton and neutron S-bands in the Xe-Ba-Ce-region

Lifetime measurements of high spin states in Yb nuclei

High spin states in128Ba