Gyromagnetic ratios of excited states in ¹⁹⁸Pt; measurements and interacting boson approximation model calculations

The enhanced transient hyperfine field manifest at the nuclei of swiftly recoiling ions traversing magnetized ferromagnetic materials was utilized to measure the gyromagnetic ratios of the 2⁺₁, 2⁺₂ and 4⁺₁ states in ¹⁹⁸Pt by the thin-foil technique. The states of interest were populated by Coulomb excitation using a beam of 220 MeV ⁵⁸Ni ions. The results obtained were: g(2⁺₁) = 0.324 ± 0.026; g(2⁺₂) = 0.34 ± 0.06; g(4⁺₁) = 0.34 ± 0.06. In addition, these measurements served to discriminate between the otherwise essentially equally probable values previously reported for the E2/M1 ratio of the 2⁺₂ → 2⁺₁ transition in ¹⁹⁸Pt. We also performed interacting boson approximation (IBA) model-based calculations in the O(6) limit symmetry, with and without inclusion of a small degree of symmetry breaking, and employed the M1 operator in both first- and second-order to obtain M1 selection rules and to calculate gyromagnetic ratios of levels. When O(6) symmetry is broken, there is a predicted departure from constancy of the g-factors which provides a good test of the nuclear wave function. Evaluative comparisons are made between these experimental and predicted g-factors.