Nuclear Chemistry Research and Spectroscopy with Radioactive Nuclei: Twenty-Third Annual Progress Report

摘要

Research supported in part by this contract has become totally devoted to the study of far-from-stable radioactive nuclei with the UNISOR facility (University Isotope Separator at Oak Ridge) on-line with HHIRF (Holifield Heavy Ion Research Facility). The purpose of these UNISOR studies is to investigate the low-spin (<21/2), low-energy (<3 MeV) nuclear structures and stability, most of which are not generally accessible by in-beam spectroscopic methods. The UNISOR facility isotope separator provides the mass selection needed for detailed nuclear spectroscopy following radioactive decay and enables one to test critically the competing theoretical concepts and calculations from nuclear models. The UNISOR studies are centered on cases where an odd valence nucleon or valence pair of nucleons act as probes of the characteristics of the core. This leads to observations of abrupt shape changes, shape coexistence, and shell-model intruder states in the region of low nuclear excitation energy. Detailed singles and gamma gamma t, e sup - gamma t, X gamma t, and alpha gamma t multiparameter coincidence measurements are carried out, and soon measurements of singles gamma -ray angular distributions and magnetic moments of mass-separated, low-temperature oriented nuclei will begin using the helium dilution refrigerator on-line to the isotope separator. In particular, what is reported centers on two neutron-deficient regions of interest, one around the Z = 82 closed shell (from Z = 77 to 85) and the other in the rare earths around the new region of deformation at N < 76 and Z > 56. 30 refs., 15 figs., 8 tabs. (ERA citation 12:044550)