Excited states in the $N=90$ and $N=91$ Pt nuclei have been investigated using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator. These nuclei were populated via the reactions ${}^{92}\mathrm{Mo}({}^{78}\mathrm{Kr},2n)$ and ${}^{94}\mathrm{Mo}({}^{78}\mathrm{Kr},3n)$ at 335 and 348 MeV, respectively. The recoil-decay tagging technique has been used to correlate prompt $\gamma$ radiation with the characteristic $\alpha$ decays of ${}^{168}\mathrm{Pt}$ and ${}^{169}\mathrm{Pt}$. A $\gamma \text{−}\gamma$ analysis has allowed a level scheme for ${}^{168}\mathrm{Pt}$ to be reported for the first time and the level scheme for ${}^{169}\mathrm{Pt}$ to be extended. The excitation energies of the proposed positive-parity yrast states of ${}^{168}\mathrm{Pt}$ are compared with calculations based on the interacting boson model and found to be in excellent agreement. These data show a continuation of the trend toward vibrational nuclei as the $N=82$ shell gap is approached. In addition, new excited states constituting two decay paths have been discovered in ${}^{169}\mathrm{Pt}$.

• Received 13 February 2009

DOI:https://doi.org/10.1103/PhysRevC.79.064314