Femtosecond laser pulses can induce desorption of oxygen adsorbed in the molecular state on Pd(111) surfaces. In this study, the behavior of the O-16(2) and O-18(2) isotopic species is characterized for the saturated Pd(111) surface at a base temperature of 95 K. The O-16(2) species is found to desorb with,a yield 1.8 +/- 0.3 times greater than that of the O-18(2) species. The implications of this finding for the desorption mechanism are discussed. (C) 2003 American, Vacuum Society.