The shape of the Tz = +1 nucleus 94Pd and the role of proton-neutron interactions on the structure of its excited states

Abstract

Reduced transition probabilities have been extracted between excited, yrast states in the 𝑁=𝑍+2 nucleus 94Pd. The transitions of interest were observed following decays of the 𝐼𝜋=14+, 𝐸𝑥=2129-keV isomeric state, which was populated following the projectile fragmentation of a 124Xe primary beam at the GSI Helmholtzzentrum für Schwerionenforschung accelerator facility as part of FAIR Phase-0. Experimental information regarding the reduced E2 transition strengths for the decays of the yrast 8+ and 6+ states was determined following isomer-delayed 𝐸𝛾1−𝐸𝛾2−△𝑇2,1 coincidence method, using the LaBr3(Ce)-based FATIMA fast-timing coincidence gamma-ray array, which allowed direct determination of lifetimes of states in 94Pd using the Generalized Centroid Difference (GCD) method. The experimental value for the half-life of the yrast 8+ state of 755(106) ps results in a reduced transition probability of B(E2:8→+6+) = 205−25+34 e2 fm4, which enables a precise verification of shell-model calculations for this unique system, lying directly between the 𝑁=𝑍 line and the 𝑁=50 neutron shell closure. The determined 𝐵(𝐸2) value provides an insight into the purity of (𝑔9/2)𝑛 configurations in competition with admixtures from excitations between the (lower) 𝑁=3𝑝𝑓 and (higher) 𝑁=4𝑔𝑑𝑠 orbitals for the first time. The results indicate weak collectivity expected for near-zero quadrupole deformation and an increasing importance of the 𝑇=0 proton-neutron interaction at 𝑁=48.