Competition between pairing correlations and deformation from the odd-even mass staggering of francium and radium isotopes

This is the authors' abstract. We don't add key points for this paper.

The masses of 222,224,226--233Fr and 233,234Ra have been determined with the Penning-trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN, including the previously unknown mass and half-life of ²³³Fr. We study the evolution of the odd-even staggering of binding energies along the francium and radium isotopic chains and of its lowest-order estimator, Δ³(N). An enhancement of the staggering of Δ³(N) is observed towards neutron number $N=146$, which points to contributions beyond pairing correlations. These contributions are investigated in the Hartree-Fock and Hartree-Fock-Bogoliubov approaches, emphasizing the connections to the single-particle level density and nuclear deformation.