Figure 3. Oxygen uptake versus exposure for molecular oxygen beam dosing of Ni(111) under four different conditions. The triangles and circles represent data for oxygen uptake obtained with 60 meV and 600 meV kinetic energy oxygen beams, respectively. The open and filled symbols represent the data for oxygen uptake on the 300 K and 120 K substrate, respectively. Note that at low substrate temperatures no oxidation is observed, even with the high energy beam.