Search for proton emission of the isomeric 10⁺ state in ⁵⁴Ni

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 ⁵⁴Ni. Excitation functions for two fusion–evaporation reactions were measured to maximise the population of the rare two-neutron evaporation channel from a ⁵⁶Ni compound nucleus. The search for delayed proton emission was based on the ²⁸Si(²⁸Si,2n)⁵⁴Ni reaction at a beam energy of 70 MeV. For this reaction, a cross-section limit for the population of the 10⁺ state in ⁵⁴Ni and its proton-decay branch was determined to be σ< 22 nb.