We discuss the use of synchrotron radiation in the photon energy range between 32 and 300 eV for performing very surface sensitive X-ray photoemission spectroscopy. The usefulness of this technique is illustrated with results for the chemisorption of oxygen on the (110) surface of both gallium arsenide (GaAs) and gallium antimonide (GaSb). Binding energy shifts in the 3d levels of gallium, arsenic, and antimony due to chemisorbed oxygen can be seen for oxygen coverages below 5 percent of a monolayer combining the surface sensitivity of Auger electron spectroscopy with the precise chemical information of X-ray photoemission spectroscopy. When oxygen is adsorbed on GaAs, charge is transferred from the surface arsenic atoms to the chemisorbed oxygen with no breaking of back bonds and, consequently, no oxidation of the surface. In GaSb, on the other hand, there is simultaneous charge transfer from both the surface gallium and antimony atoms, indicating that back bonds are broken and oxide formation is taking place. The escape depth for GaAs (110) was also measured for electron kinetic energies between 20 and 200 eV.