The photodesorption of oxygen admolecules was studied on a stepped Pt(113) = (s)2(111) x (001) surface with 193 nm irradiation at 110 K. Multidirectional desorptions were found to collimate at +/- 12 - 20 degrees and +/- 45 - 49 degrees off the surface normal and also along the surface normal in a plane along the trough. The first component is always dominant, and the weak second component only appears at higher oxygen coverages. The normally directed desorption is not significant. The translational energy of desorbing O-2 peaks around 15-20 degrees and 50 degrees, confirming the inclined desorptions. It is proposed that these inclined components are due to the desorption induced by the impact of oxygen admolecules with hot oxygen atoms from the photodissociation of adsorbed molecular oxygen, emitted along the trough. A simple cosine distribution was found to fit the thermal desorption from oxygen admolecules and also the recombinative desorption of oxygen adatoms. The 193 nm irradiation also produces additional, less tightly bound oxygen adatoms, which yield a desorption component collimated at 15 degrees from the surface normal in the step-down direction.