Low-lying structure of light radon isotopes
Аннотация
The excited states in the neutron-deficient isotopes ${}^{200,202,204}\mathrm{Rn}$ have been populated using the ${}^{168}\mathrm{Er}{(}^{36}\mathrm{Ar},4n),{}^{166}\mathrm{Er}{(}^{40}\mathrm{Ar},4n),$ and ${}^{168}\mathrm{Er}{(}^{40}\mathrm{Ar},4n)$ 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 $\ensuremath{\gamma}$ 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-$\ensuremath{\gamma}$ and recoil-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidences were used to construct decay schemes of light radon isotopes. Measurements of delayed $\ensuremath{\gamma}$ rays at the focal plane have also been made, and microsecond isomers have been observed in ${}^{200,202}\mathrm{Rn},$ but not in ${}^{204}\mathrm{Rn}.$ Comparison of the results with those for polonium isotopes indicate a common mechanism for the onset of deformation. Candidates have been found in ${}^{202,204}\mathrm{Rn}$ for deformed intruder states which coexist with the spherical ground-state shape.