Simple interpretation of shape evolution in Pt isotopes without intruder states

The most commonly accepted interpretation of the light Pt isotopes invokes the coexistence and mixing with proton intruder states from above the Z = 82 shell gap. Using an alternative description, interacting boson model (IBA) calculations are performed for the Pt isotopes with a simple, single configuration, two-parameter Hamiltonian. Excellent agreement is obtained for energies and electromagnetic transition strengths over the entire isotopic chain, spanning a wide variety of structures, and suggesting that these nuclei can be described more simply without the introduction of an intruder configuration. The Pt nuclei close to midshell are found to lie close to a region of phase/shape coexistence.