  Combining laser spectroscopy in a Versatile Arc Discharge and Laser Ion
Source, with Penning-trap mass spectrometry at the CERN-ISOLDE facility, this
work reports on mean-square charge radii of neutron-rich mercury isotopes
across the $N = 126$ shell closure, the electromagnetic moments of $^{207}$Hg
and more precise mass values of $^{206-208}$Hg. The odd-even staggering (OES)
of the mean square charge radii and the kink at $N = 126$ are analyzed within
the framework of covariant density functional theory (CDFT), with comparisons
between different functionals to investigate the dependence of the results on
the underlying single-particle structure. The observed features are defined
predominantly in the particle-hole channel in CDFT, since both are present in
the calculations without pairing. However, the magnitude of the kink is still
affected by the occupation of the $1i_{11/2}$ and $2g_{9/2}$ orbitals with a
dependence on the relative energies as well as pairing.
