Laser induced charge transfer (CT) processes have attracted attention for many years. These reactions play an important role in chemistry as well as biophysics and biology. When the reaction is induced by laser on a complex formed in a supersonic beam, the impact geometry is well defined and reaction details are more evident. This paper deals with features relevant to O-2 photodissociation induced in clusters of oxygen molecules and rare gases, water or organic molecules. Our studies, performed in a supersonic beam by using lasers of different wavelength to induce the reaction and to detect the reaction products by multiphoton ionization, show that production of atomic oxygen is strongly dependent on the ionization potential of the electron donor.