A newly observed isomeric intruder 1 /2 + state [T1 /2 = 3.5(6) ms] is identified in 203 At using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of E3 and mixed M1/E2 transitions to the 9 /2 − ground state, and it is suggested to originate from the π (s1 /2 ) −1 configuration. In addition, the structures above the 1 /2 + state in 203 At and 197 At are studied using in-beam γ -ray spectroscopy, recoil-decay tagging, and recoil-isomer decay tagging methods. The 1 /2 + state is fed from 3 /2 + and 5 /2 + states, and the origin of these states are discussed.
The extremely neutron-deficient isotope 178 Pb has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the α decay of 178 Pb and its α-decay chain through α-α correlations. The α decay was measured to have an energy and half-life of E α = 7610(30) keV and t 1/2 = 0.21−0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The α-decay reduced width and hindrance factor for 178 Pb were deduced and correspond to an unhindered l = 0 transition. In addition, the mass excess of 178 Pb and the α-decay Q value were calculated from the experimental results and compared to theoretical values.
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