Decay spectroscopy of Pb-179(82)97 and evidence for a 9/2(-) intruder state in Tl-179(81)98

The very neutron-deficient isobars Pb-179 and Tl-179 have been produced using the fusion-evaporation reactions Pd-104(Kr-78,xpyn), where x <= 1 and y >= 2. The gas-filled separator RITU was employed to transport and separate the recoiling nuclei of interest from the scattered beam and unwanted products. The GREAT spectrometer was used to study the decay properties through alpha-alpha and alpha-gamma correlations, which has allowed the ground state of Pb-179 to be assigned as I-pi = 9/2(-). The decay of Pb-179 was measured to have an alpha-particle energy and half-life of E-alpha = 7348(5) keV and t(1/2) = 2.7(2) ms, respectively. A search for a nu i(13/2) state in Pb-179 was performed, but only a limit of excitation energy and half-life was obtained. In Tl-179 a t(1/2) = 114(-10)(+18) ns isomeric state, likely at an excitation energy of 904.5(9) keV, was identified and is tentatively assigned to be a 9/2(-) proton intruder state.