Benchmarking the PreSPEC@GSI Experiment for Coulex-multipolarimetry on the π(p_3/2) → π(p_1/2) spin-flip transition in ⁸⁵Br

A first performance test of the Coulomb excitation multipolarimetry (Coulex-multipolarimetry) method is presented. It is based on a 85Br π(p3/2) → π(p1/2) spin-flip experiment performed as part of the PreSPEC-AGATA campaign at the GSI Helmholtzzentrum für Schwerionenforschung (GSI). Via determination of background levels around the expected 85Br excitations as well as measured 197Au excitations, an upper limit for the M1 transition strength of the 1/2⁻₁ → 3/2⁻g.s. transition in 85Br and a lower beam time limit for upcoming experimental campaigns utilizing Coulex-multipolarimetry have been inferred. The impact of the use of AGATA in its anticipated 1π configuration on these estimates is deduced via Geant4 simulations