Optically enhanced oxidation of GaAs is promising both for insight into fundamental mechanisms of oxygen chemisorption and for possible application in GaAs direct write. For atomically clean GaAs(110), we have found that sample temperature is a key parameter in determining the increase of oxygen uptake under low-intensity argon ion laser illumination (1 W/cm2 at 2.41 eV) relative to the ‘‘dark’’ uptake. Although cooling to 185 K suppresses the dark oxygen adsorption rate, the oxygen uptake with optical irradiation is the same at both 185 and 400 K. The ratio of laser-assisted to dark uptake for 108 L exposure then approaches the enhancement necessary for spatially selective oxidation, showing an increase from 2.5 at room temperature to well over 10 at 185 K. After ruling out sample heating and direct oxygen gas excitation, we suggest that the light-induced increase in uptake is due to electronic excitations in the GaAs. To explain the enhancement, one also needs to assume a weakly adsorbed precursor state that converts to the chemisorption state when thermally or optically activated; the implications for previously suggested oxidation mechanisms will be discussed.