Singlet atomic oxygen Rydberg states of the (D-2) 3d’ configuration have been observed as three-photon resonances. The states Lie above the first ionization energy but are forbidden to autoionize in LS coupling. All transitions originated from the metastable p(4) D-1(2) state produced by laser photolysis of ozone at similar to 276 nm. The same laser pulse was used to ionize the atoms. Arrival time spectra of the atomic photofragment have also been recorded.