Low-lying structure of light radon isotopes

Abstract

The excited states in the neutron-deficient isotopes Rn have been populated using the Er(Ar,4n), Er(Ar,4n), and Er(Ar,4n) reactions at beam energies of 175, 182, and 177 MeV, respectively. Evaporation residues were selected using an in-flight gas-filled separator and implanted at the focal plane into a 16-element position-sensitive, passivated ion-implanted planar silicon detector. Prompt γ rays were observed at the target position using an array of Compton-suppressed germanium detectors. Correlation with the subsequent radioactive decay of associated recoiling ions in the silicon detector, recoil-γ and recoil-γ-γ coincidences were used to construct decay schemes of light radon isotopes. Measurements of delayed y rays at the focal plane have also been made, and microsecond isomers have been observed in Rn, but not in Rn. Comparison of the results with those for polonium isotopes indicate a common mechanism for the onset of deformation. Candidates have been found in Rn for deformed intruder states which coexist with the spherical ground-state shape.