Reply to "Oxidation properties of GaAs (110) surfaces" by R. Ludeke

We show that the chemisorption of oxygen on the GaAs (110) surface results in a single oxygen bonded to the surface As atoms with no breaking of back bonds. The disappearance at ${10}^7$langmuirs ${\mathrm{O}}_2$ of the partial yield (and electron energy loss) structure from the Ga $3d$ to surface-state excitonic transition is due to large changes in the surface electronic structure rather than direct chemisorption of oxygen onto the surface gallium atoms.