Electromagnetic properties of low-excitation states in ¹⁹¹Ir and ¹⁹³Ir and supersymmetry schemes

The electromagnetic properties of low-excitation states in ¹⁹¹Ir and ¹⁹³Ir have been studied following Coulomb excitation. Gyromagnetic ratios were measured by the transient-field technique and level lifetimes were measured by the Doppler-shift recoil distance method. Multipolarity mixing ratios were determined from measured particle-γ angular correlations. The present lifetime and g-factor results extend the data available for comparison with theory and help discriminate between disparate experimental values reported previously in the literature. We compare the experimental data with particle-triaxial-rotor model calculations and with the predictions of the U(6/4) and U(6/20) supersymmetry models based on the interacting-boson-fermion model.