Laser spectroscopy measurements have been carried out on very-neutron-deficient platinum isotopes with the COMPLIS experimental setup. Using the ${5d}^9{6s}^3{D}_3\to {5d}^9{6p}^3{P}_2$ optical transition, hyperfine spectra of ${}^{182,181,180,179,178}\mathrm{Pt}$ and ${}^{183}{\mathrm{Pt}}^m$ 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 ${}^{183}{\mathrm{Pt}}^m$ were thus measured. A large deformation change between ${}^{183}{\mathrm{Pt}}^g$ and ${}^{183}{\mathrm{Pt}}^m,$ an odd-even staggering of the charge radius, and a deformation drop from $A=179\mathrm{}$ are clearly observed. Comparisons are made with microscopic theoretical predictions, in particular Hartree-Fock-Bogoliubov calculations using the Gogny force.

• Received 28 April 1998

DOI:https://doi.org/10.1103/PhysRevC.60.054310