Study of The N = 77 Isotones Near The Proton-drip Line; Isomeric Decays of ¹⁴⁰Eu, ¹⁴²Tb, ¹⁴⁴Ho, and ¹⁴⁶Tm

In this dissertation, the systematics of the [pi]h₁₁/₂ [tensor] [nu]h₁₁/₂ and [pi]h₁₁/₂ [tensor] [nu]s₁/₂ 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 I[pi] = 8⁺ and 5⁻ were deduced for the isomers in ¹⁴⁰ Eu 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) [mu]s 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 ¹⁴⁶gsTm, 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 the deformation and proton and neutron coupling to the core excitations. A complex wave function structure was obtained, with dominating components of [pi]h₁₁/₂ [tensor] [nu]h₁₁/₂ for the10⁺ isomer and [pi]h₁₁/₂ [tensor] [nu]s₁/₂ 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.