Single proton structure of Ir193,195,197 and perturbed spin(6) symmetry

The Pt194,196,198(t)Ir193,195,197 reactions have been studied with a 17 MeV polarized triton beam. Based on the measured angular distributions of cross sections and analyzing powers, several new Iassignments were made in Ir195 and new levels were identified in Ir197. The change in the distribution of d32 spectroscopic strength as a function of neutron number is observed to be quite dramatic. Two large fragments are observed in Ir193, all of the d32 strength is concentrated in the ground state of Ir197, and Ir195 shows a situation intermediate between these two. The empirical d32 strength in Ir193 is well reproduced by the predictions of the U(64) supersymmetry proposed for the Os-Ir-Pt nuclei. The change in the d32 strength as a function of neutron number is well reproduced by a perturbation of this symmetry. NUCLEAR REACTIONS Pt194,196,198(t), Et=17 MeV, enriched targets; measured (E+), Ay(E+). Ir193,195,197 deduced levels, I, spectroscopic strengths. NUCLEAR STRUCTURE Interacting boson fermion model, U(64) supersymmetry, spin(6) symmetry.