In the present work, we report the 25 MeV oxygen irradiation effects in n-type single crystal β-GaO at different fluences. We demonstrate that the symmetric stretching modes and bending vibrations of GaO and GaO units are impaired upon increasing O irradiation fluence. Blue and green photoluminescence (PL) emission bands are found to be mainly associated with gallium-oxygen divacancies, gallium vacancies and oxygen interstitials. The increase of optically active centers at low fluence and the PL quenching at high fluence are ascribed to the reduction of carrier density and the production of non-radiative recombination centers, respectively. The results envisage the possibility of obtaining pre-designed spectral behaviors by varying the oxygen irradiation fluence.