Laser-ablated nickel atoms react with dioxygen to form the primary oxides NiO and ONiO, some of which combine to form the secondary oxides Ni2O2 and ONiONiO during condensation in excess argon at 10 K. The insertion product dioxide ONiO is linear based on natural nickel and O-18 isotopic substitution and DFT calculations. Annealing produces the cyclic adducts reported in earlier thermal nickel experiments and the new NiOO superoxide species, which are characterized by isotopic shifts and DFT structure and frequency calculations. In addition, dioxygen complexes with NiO and ONiO were also observed. Finally, the matrix provides sharp bands and the resolution to observe nickel isotopic splittings which characterize the Fermi-resonance interaction in the ONiOO and (O-2)Ni(O2) molecules.