Search for proton emission of the isomeric $$\mathbf {10^+}$$10+ state in $$\mathbf {^{54}}$$54 Ni

Several experiments were conducted at the 10 MV Van-de-Graaff tandem accelerator at the Institute of Nuclear Physics, Cologne, to detect proton emission from the isomeric 6457-keV \(10^+\) state in \(^{54}\hbox {Ni}\). Excitation functions for two fusion–evaporation reactions were measured to maximise the population of the rare two-neutron evaporation channel from a \(^{56}\hbox {Ni}\) compound nucleus. The search for delayed proton emission was based on the \(^{28}\hbox {Si}\)(\(^{28}\hbox {Si},2n\))\(^{54}\hbox {Ni}\) reaction at a beam energy of 70 MeV. For this reaction, a cross-section limit for the population of the \(10^+\) state in \(^{54}\hbox {Ni}\) and its proton-decay branch was determined to be \(\sigma < 22\) nb.