First observation of the β decay of neutron-rich 218Bi by the pulsed-release technique and resonant laser ionization

Abstract

The neutron-rich isotope 218Bi has been produced in proton-induced spallation of a uranium carbide target at the ISOLDE facility at CERN, extracted from the ion source by the pulsed-release technique and resonant laser ionization, and its β decay is studied for the first time. A half-life of 33(1)s was measured and is discussed in the self-consistent continuum-quasi particle-random-phase approximation framework that includes Gamow-Teller and first-forbidden transitions. A level scheme was constructed for 218Po, and a deexcitation pattern of stretched E2 transitions 8 + → 6+ → 4+ → 2+ → 0+ to the ground state is suggested. Shell-model calculations based on the Kuo-Herling interaction reproduce the experimental results satisfactorily.