Isomers in Tl 203 and core excitations built on a five-nucleon-hole structure

Isomers with three- and five-nucleon-hole configurations have been established in Tl203. These include newly identified levels with a three-nucleon-hole structure: Iπ = (15/2-) with T1/2 = 7.9(5) ns and Iπ = (35/2-) with T1/2 = 4.0(5) ns. In addition, five-nucleon-hole states have also been established: Iπ = (39/2-) with T1/2 = 1.9(2) ns and Iπ = (49/2+) with T1/2 = 3.4(4) ns. The previously determined long-lived decay, T1/2 = 6.6(3) μs from this work, is associated with isomerism of the Iπ = (29/2+) state. Levels above this long-lived isomer have been identified through a delayed-prompt γ-γ coincidence measurement. Five-nucleon-hole states with excitation energies Ex≈ 7 MeV have been established as well as possible octupole excitations of the Pb208 core built on these levels. The level scheme of Tl203 is extended up to Ex≈ 11 MeV with the inclusion of 25 new transitions. Empirical and shell-model calculations have been performed to aid in the description of the observed states which are found to be of intrinsic character.