Decay spectroscopy of Pb97 1 82179 and evidence for a 9/2- intruder state in Tl98 1 81179

Abstract

The very neutron-deficient isobars Pb179 and Tl179 have been produced using the fusion-evaporation reactions Pd104(Kr78,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 α-α and α-γ correlations, which has allowed the ground state of Pb179 to be assigned as Iπ=9/2-. The decay of Pb179 was measured to have an α-particle energy and half-life of Eα=7348(5)keV and t1/2=2.7(2) ms, respectively. A search for a νi13/2 state in Pb179 was performed, but only a limit of excitation energy and half-life was obtained. In Tl179 a t1/2=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.