Collective states in Pt198 and models for shape transitional nuclei

Studies of the (n,n′) and (n,n′γ) reactions, together with other recent data, delineate the level and decay schemes for collective levels of Pt198 below 1.5 MeV excitation energy. The level scheme, which approximates that of an anharmonic vibrator, is consistent with boson expansion theory calculations. These calculations place Pt198 naturally in a systematic development of nuclear structure through the Pt isotopes and explain the γ-ray decay intensities of excited levels. The O(6) limit of the interacting boson model, on the other hand, appears inappropriate for Pt.198 NUCLEAR REACTIONS Pt198(n,n′γ), En=0.8-2.5 MeV, Pt198(n,n′). En=1.68 MeV; measured Eγ, Iγ, σ(E;Eγ,125°), σ(Eγ, θγ), σ(En,θ). Deduced levels, J, π. Compared to boson expansion theory and interacting boson model. Enriched target, time-of-flight neutron detection.