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

Abstract

The masses of 222,224,[226][227][228][229][230][231][232][233]234 Ra 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 233 Fr. 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, 3 (N ). An enhancement of the staggering of 3 (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.

Laser-spectroscopy studies of the nuclear structure of neutron-rich radium

“…In contrast to the francium odd-even staggering whose D(N ; δ r 2 ) parameter displays a sudden increase at N = 139,140, the radium isotopes display no such strong increase, instead continuing a smooth upward trend with increasing neutron number. This increased oddeven staggering agrees with the behavior seen in the binding energies of these isotopes [31]. Here, the enhanced odd-even staggering towards N = 146 was reproduced by both Hartree-Fock and Hartree-Fock-Bogoliubov calculations by increasing quadrupole deformation.…”

“…The increasing magnitude of the intrinsic quadrupole moments adds further experimental support to the calculations presented in Ref. [31].…”

In-Source Laser Spectroscopy with the Laser Ion Source and Trap: First Direct Study of the Ground-State Properties ofPo217,219

“…The francium ions cover a wide range of masses, from A ¼ 200 [44] to 233 [45]. Their yields vary from < 1 to > 10 8 atoms per second, depending on the reaction cross section, the diffusion and effusion properties of the target, and the half-life of each isotope [46].…”

Prominence of Pairing in Inclusive (p,2p) and (p,pnPaul1, Obertelli2, Bertulani3 et al. 2019Phys. Rev. Lett.7030View full textAdd to dashboardCite

“…When separation energies are low, this effect becomes prominent, as ∆ p represents a significant fraction of S n (∼ 40% for the even-Z daughter nuclides considered here). The above gap is quantitatively valid for spherical nuclei, but may be distorted in exotic nuclei by correlations such as deformation, see for example [59]. Nevertheless, that even-Z nuclei have a lower level density for proton-driven states than odd-Z nuclei remains true [60].…”

“…Nevertheless, that even-Z nuclei have a lower level density for proton-driven states than odd-Z nuclei remains true [60]. As a quantitative illustration of a specific case, we consider here the strength distribution in the neighboring 59 Co and 58 Fe stable nuclei after one proton transfer (d, 3 He) as published in [61,62]. The ratio of their respective integrated spectroscopic strengths up to 1 MeV is 0.3, with more strength at low energy for 59 Co than for 58 Fe.…”