SINGLE-NUCLEON-TRANSFER TESTS OF THE U(6/12) SUPERSYMMETRY IN PLATINUM ISOTOPES

Levels in 197,199Pt have been studied using the 198Pt(d,t)197Pt, 198Pt(d, p)199Pt and 196,198Pt(t, d)197,199Pt reactions with 18 MeV deuterons and tritons. The charged particle spectra were analysed with a magnetic spectrometer. Spins and parities have been determined from angular distributions of cross sections and analysing powers for over 20 levels in 197Pt and for 8 in 199Pt. For many levels the spin values were previously ambiguous, but tentative assignments had been adopted to fit the U( 6 12) scheme. The present work supports the spin-parity values chosen in that interpretation for almost all levels in 197,199Pt. A new analysis of single-nucleon transfer strengths for 193,195,197,199Pt levels has also been performed and compared with U( 6 12) predictions. A chi-square test was applied to the fitted strengths to obtain a goodness-of-fit parameter which takes into account the large number of fitted parameters in this model. If one considers only the 1 2-, 3 2- and 5 2- levels the U( 6 12) description is acceptable for 195Pt but This is consistent with the intuitive conclusion reached from the large observed strengths for some transitions that are forbidden in the model. Also, there are systematic findings of large strengths to 7 2- levels assigned in terms of the U( 6 12) model, suggesting a need for this model to be extended. © 1990.