Interacting boson approximation-2 analysis of the Pd and Ru chains. II. Mixed symmetry states ofF<Fmax−1character in even palladium and ruthenium isotopes

Abstract

The interacting boson approximation-2 analysis of even ${}^{100\ensuremath{-}116}\mathrm{Pd}$ and ${}^{98\ensuremath{-}114}\mathrm{Ru}$ isotopes, which led us to the identification of whole groups of ${F=F}_{\mathrm{max}}\ensuremath{-}1$ states, has been extended to check whether states of $Fl{F}_{\mathrm{max}}\ensuremath{-}1$ character could also be present in these isotopic chains. To have a guideline for their identification we performed numerical calculations in the U(5) limit of the model and found that for three groups of ${F=F}_{\mathrm{max}}\ensuremath{-}2$ states the generalized Majorana operator eigenvalues can be expressed in analytic form. The information derived on the excitation-energy pattern of these states has been exploited to account for the possibility that mixed symmetry (MS) states with $Jg~8$ are yrast in the realistic cases considered. A first hint for the identification of MS states having large $Fl{F}_{\mathrm{max}}\ensuremath{-}1$ components at energies lower than 5.5 MeV has been obtained from the comparison of the experimental and calculated energies for the relevant states in both palladium and ruthenium chains. The analysis of the available data on their e.m. properties (mixing ratios and intensity ratios) supports this interpretation.