Study of the N = 77 isotones near the proton-drip line: Isomeric decays of europium-140, terbium-142, holmium-144, and thulium-146.

摘要

In this dissertation, the systematics of the pih 11/2 ⊗ nuh11/2 and pi h11/2 ⊗ nus1/2 isomeric configurations were studied for the odd-Z, N = 77 isotones near the proton drip line. The isomeric decays in 140Eu, 142Tb, 144Ho and 146Tm were measured by means of X-ray, gamma-ray and charged particle spectroscopy at the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility ( HRIBF) at Oak Ridge National Laboratory (ORNL). The spin and parity of Ipi = 8+ and 5- were deduced for the isomers in 140Eu and 142Tb. New decay schemes were established, and the half-lives of the 8+ isomers were measured to be 302(3) ns for 140m2Eu and 25(1) mus for 142m2Tb. No evidence for the expected 1+ ground-state was found in the 144Ho decay data.;The proton emission from 146Tm was restudied. Five proton transitions were assigned to two proton emitting states. The half-lives of 198(3) ms and 68(3) ms and the spin and parity values of I pi = 10+ and 5- were established for 146mTm and 146 gsTm, respectively. For the first time for an odd-odd nucleus, the interpretation of the observed decay properties and structure of the proton-emitting states was made by accounting for deformation and proton and neutron coupling to the core excitations. A complex wave function structure was obtained, with dominating components of pih11/2 ⊗ nu h11/2 for the 10+ isomer and pi h11/2 ⊗ nus1/2 for the 5- ground state.;Details of the experimental setup and results as well as a brief description of the detectors used in the experiments and the HRIBF facility will be discussed in this dissertation.