Spectroscopic studies on high-spin states in ¹⁷⁹ ¹⁸¹Ir and ¹⁷⁵Re

High-spin states of the odd-A ^179,181Ir and ¹⁷⁵Re were studied at the Oak Ridge Holified Heavy-Ion Research Facility. In these experiments the heavy-ion fusion reactions ^156,158Gd(²⁷Al,4n) and ¹⁵⁶Gd(²³Na,4n) were used. Rotational bands built on various single proton states have been established for these three nuclei, among which the level structures of ¹⁷⁹Ir and ¹⁷⁵Re were totally unknown prior to this work. The previously studied structure of ¹⁸¹Ir has been extended to higher spins. Bands built on the πh_9/2 (½^-[541]), πi_13/2 (½⁺[660]), π,i>d_5/2 (5/2⁺[402]) and πh_11/2 (9/2^-[514]) states have been observed in all three nuclei. The πƒ_7/2 (½^-[530]) band in ¹⁷⁹Ir and πg_7/2 (7/2⁺[404]) band in ¹⁷⁵Re were established for the first time in Ir and Re nuclei. The particle-rotor model was applied to the electromagnetic properties of the strongly-coupled bands. The calculations were compared with the experimentally extracted B(M1;I → I — 1)/B(E2; I → I — 2) ratios and a good agreement was found, which in turn supports the band assignments. As a by-product of the ¹⁷⁹Ir experiment, a preliminary decay scheme of the odd-odd ¹⁷⁸Ir has been established. The reaction ¹⁵⁶Gd(²⁷Al,5n) was used in the measurement. Five band structures have been assigned to this nucleus. Among them three rotational sequences have been identified as bands built on the semi-decoupled πh_9/2⊗vi_13/2, the doubly-decoupled π½^-[541]⊗v½^-[521], and the strongly-coupled πh_11/2⊗vi_13/2 structures. From the thesis work, it is found that the intruder πh_9/2 and πi_13/2 states play very important roles in determining the nuclear properties of Ir and Re nuclei. Three important aspects associated with the intruder states have been realized and discussed as: (1) large deformation driving, (2) shape evolution, and (3) band crossing. The nuclear shapes have been studied in the framework of Total Routhian Surface calculations. Standard Cranked Shell Model calculations have been performed to investigate the bandcrossing phenomena in Re-Ir-Au nuclei. The discrepancy between theoretical predictions and experiments has been recognized, and a few suggestions of its origin have been made.