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