Large odd-even radius staggering in the very light platinum isotopes from laser spectroscopy

Laser spectroscopy measurements have been carried out on very-neutron-deficient platinum isotopes with the COMPLIS experimental setup. Using the 5d⁹6s³D₃→5d⁹6p³P₂ optical transition, hyperfine spectra of 182,181,180,179,178Pt and ¹⁸³Ptᵐ were recorded for the first time. The variation of the mean square charge radius between these nuclei, the magnetic moments of the odd isotopes, and the quadrupole moment of ¹⁸³Ptᵐ were thus measured. A large deformation change between ¹⁸³Ptᵍ and ¹⁸³Ptᵐ, an odd-even staggering of the charge radius, and a deformation drop from $A=179$ are clearly observed. Comparisons are made with microscopic theoretical predictions, in particular Hartree-Fock-Bogoliubov calculations using the Gogny force.