Shape staggering of midshell mercury isotopes from in-source laser spectroscopy compared with density-functional-theory and Monte Carlo shell-model calculations

Sels, S.*; Day Goodacre, T.*; Marsh, B. A.*; Pastore, A.*; Ryssens, W.*; 角田 佑介*; Althubiti, N.*; Andel, B.*; Andreyev, A. N.; 他39名*

Physical Review C, 99(4), p.044306_1 - 044306_17, 2019/04

https://doi.org/10.1103/PhysRevC.99.044306

Neutron-deficient Hg isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring the isotope shifts and hyperfine structures of Hg. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole, and electric quadrupole moments of the odd- isotopes and arguments in favor of spin assignment for Hg were deduced. Experimental results are compared with density functional theory (DFT) and Monte Carlo shell model (MCSM) calculations. DFT calculations using Skyrme parametrizations predict a jump in the charge radius around the neutron midshell, with an odd-even staggering pattern related to the coexistence of nearly degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiments out of reach for current functionals. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: a substantial change in occupancy of the proton and neutron orbitals.