Abstract The dynamics of the UV-photochemistry of molecularly adsorbed oxygen on Pd(111) has been studied using pulsed laser light between 3.9 and 6.4 eV photon energy. Photodissociation to form atomic surface oxygen and photodesorption of O2 are the primary processes. The latter is characterized by a translational energy of about 800 K indicating non-thermal desorption. Since the photolytically formed atomic oxygen competes with the molecular adsorbate for binding sites some of the latter is displaced. This manifests itself in a conversion process between adsorbate states and in a desorption channel with a translational energy of 120 K indicating accommodation to the surface temperature. The cross sections for all processes rise exponentially from 3.9 to 6.4 eV by a factor of 38.