Measured magnetic moments of 21+ states in 190-198Pt and interacting boson model description of M1 systematics in the platinum isotopes

The g-factor of the 21+ state in 190Pt has been measured for the first time using the thin-foil transient-field technique with a target enriched (to 4.19%) in 190Pt. Precessions for the 21+ states of 190,192,194,196,198Pt were measured simultaneously. The Coulomb excitation cross section to the 21+ state in 190Pt was also measured relative to the 01+ →21+ excitations in 194Pt and 196Pt. The near constancy of g(21+) for the even 190-198Pt isotopes is in marked contrast with the behaviour observed in neighbouring even 182-186W and 186-192Os nuclei and the predictions of the proton-neutron interacting boson model in the limit of F-spin symmetry. It is shown that the observed g-factor and M1 transition systematics in the Pt isotopes can be described by appropriate F-spin symmetry breaking, while maintaining satisfactory descriptions of the energy levels and E2 properties. (orig.)