Coulomb excitation of $^{222}$Rn

International audienceThe nature of quadrupole and octupole collectivity in $^{222}$Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive $^{222}$Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball $\gamma$ -ray spectrometer following the bombardment of two targets, $^{120}$Sn and $^{60}$Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10 ¯h and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) $e$ fm$^2$ . The values of the intrinsic electric-octupole moment for the $0^+ \to 3^-$ and $2^+ \to 5^-$ transitions were found to be respectively $2360^{+300}_{-210}$ $e$ fm$_3$ and $2300^{+300}_{-500}$ $e$ fm$^3$ while a smaller value, $1200^{+500}_{-900}$ $e$ fm$^3$ , was found for the $2^+ \to 1^-$ transition. In addition, four excited non-yrast states were identified in this work via γ -γ coincidences