Investigation of isub(13/2) excitations in 197Hg and 191Pt

The level schemes of the odd-neutron nuclei 197Hg and 191Pt have been studied using in-beam spectroscopic methods. Energies, intensities, angular distributions and coincidences of the γ-rays following (α, 2n) reactions were measured. Also conversion electrons and delayed γ-ray spectra were recorded. Most of the levels in both nuclei are de-populated via the (13/2)+ isomers. Besides the yrast states, several additional states with spin values between (13/2) and (21/2) were identified. The negative parity of a side band in 197Hg starting with an I = (21/2) state was proved by the conversion electron measurement. The families of positive-parity states were compared with model calculations where the core was described as rigid triaxial rotor or anharmonic vibrator. For 197Hg both models give similarly good results for the energy spectrum and the branching ratios of electromagnetic transitions. Several negative-parity states found in 197Hg are compared with the predictions of a pairing-plus-quadrupole model. (Auth.)