Do nuclei go pear-shaped? Coulomb excitation of 220Rn and 224Ra at REX-ISOLDE (CERN)

The IS475 collaboration conducted Coulomb-excitation experiments with post-accelerated radioactive 220 Rn and 224 Ra beams at the REX-ISOLDE facility. The beam particles (Ebeam: 2.83 MeV/u) were Coulomb excited using 60 Ni, 114 Cd, and 120 Sn scattering targets. De-excitation -rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured -ray yields. The extracted ⟨3 - ||E3||0 + ⟩ matrix element allows for the conclusion that, while 220 Rn represents an octupole vibrational system, 224 Ra has already substantial octupole correlations in its ground state. This finding has implications for the search of CP-violating Schiff moments in the atomic systems of the adjacent odd-mass nuclei.