UV irradn. (hv = 3.9 to 6.4 eV) of O2 adsorbed on Pd (111) induces photodesorption and photodissocn. Both processes are of non-thermal character. Moreover, thermal conversion processes between adsorbate states are obsd. and be coupled to a thermal desorption channel. As the incident photon energy is raised from 3.9 eV to 6.4 eV, the cross sections for all processes rise exponentially by a factor of 38. Angle resolved measurements with respect to the polar and azimuthal desorption angle show that desorption flux and translational energy carry information about the adsorbate binding geometry prior to desorption.