The shape of the <i>T</i>_z = +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+34 −25 e2fm4 , 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 = 3 pf and (higher) N = 4 gds 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