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

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 I ^π=14 ⁺, E _x=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 E _{γ 1}−E _{γ 2}−△T _2,1 coincidence method, using the LaBr ₃(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 e ² fm ⁴, 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 (g _9/2) 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.