Dipole magnetic bands in the frontiers of nuclear structure

• Grant number: 03/07356-3
• Support Opportunities: Research Projects - Thematic Grants
• Start date: December 01, 2003
• End date: February 28, 2006
• Field of knowledge: Physical Sciences and Mathematics - Physics - Nuclear Physics
• Principal Investigator: Roberto Vicençotto Ribas
• Grantee: Roberto Vicençotto Ribas
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The investigation of magnetic rotation and of chiral bands, both predicted by Tilted Axis Crankin9 (TAC) model calculations, are presently two of the most relevant subjects of nuclear structure research. The first is related to the breaking of rotational symmetry by the current distribution in nearly spherical nuclei, while the second is related to the breaking of the left-right symmetry in the intrinsic system of triaxial nuclei. The TAC model (created by S. Frauendorf) is a generalization of the Cranking model for a rotational axis tilted with respect to the principal axes of the moment of inertia of a deformed nucleus. It is particularly suited for the description of high-K (the projection of the total angular momentum on the longest deformation axis) bands, which are characterized by magnetic dipole transitions and negligible or absent signature splitting. Magnetic rotation is characterized by the existence of rotational-like bands in nearly spherical nuclei, also known as shears bands, and has already been observed and studied in various regions of the nuclide chart. On the other hand, in a few regions of triaxially deformed nuclei, valence particles and boles and collective angular momenta tend to align at high spin along the three perpendicular axes of the deformed core, breaking chiral symmetry. Chiral bands appear experimentally as a pair of nearly degenerate Ml bands, and have only been reportedly observed in the A ~ 130 region. They are also predicted for the triaxial nuclei aroundlo6Ru, where the active high-j orbits are h11/2 for neutrons and g9/2 boles for protons. However, the production of these neutron-rich nuclei is difficult or impossible by standard fusion-evaporation reactions with stable isotopes. Several magnetic dipole bands have already been observed in the A ~ 100 mass region, particularly in the neutron deficient side, more easily accessible. Some of these bands, in weakly deformed nuclei, have been interpreted as magnetic rotation. The region is transitional and therefore rich in variety of nuclear deformations.We propose to study the high-spin nuclear states of 104,106Rh, 103,104Ru, e 106Pd, among others, by in-beam gamma-ray spectroscopy of heavy-ion reactions at the Pelletron accelerator of the Laboratório Aberto de Física Nuclear (LAFN), IFUSP-DFN... (AU)