In-beam γ rays have been observed in the neutron-deficient isotopes ${}^{170,171,172}\mathrm{Pt}$ using the recoil-decay tagging technique. The yrast transition sequence proposed for ${}^{172}\mathrm{Pt}$ indicates that the $0^{+}$ bandhead of the deformed intruder band is situated about 900 keV above the weakly deformed ground state, i.e., its excitation energy has risen by about 300 keV compared to ${}^{174}\mathrm{Pt}.$ The measured energy of the $2^{+}\to 0^{+}$ transition in ${}^{170}\mathrm{Pt}$ supports an even larger increase in the excitation energy of the intruder configuration with the departure from the middle of the 82–126 major neutron shell. Furthermore, a band with transition energies almost identical to those found in ${}^{172}\mathrm{Pt}$ has been assigned to ${}^{171}\mathrm{Pt}$ and was interpreted as corresponding to a rotationally aligned $i_{13/2}$ neutron orbital coupled to the core excitations.

• Received 22 June 1998

DOI:https://doi.org/10.1103/PhysRevC.58.2710