The interaction of O(2) with gold foil and gold nanoparticles grown by thermal deposition on TiO(2)(110) was studied by in situ ambient pressure X-ray photoelectron spectroscopy at room temperature. No spontaneous dissociation of O(2) was observed either on Au foil or on Au nanoparticles up to 1 Torr of O(2). X-ray irradiation, however, is very effective in promoting gold oxidation on both surfaces in the presence of O(2). Our results help reconcile recent conflicting experimental observations regarding the activation of molecular oxygen, which is a crucial issue in Au catalyzed oxidation reactions.