In this work we correlate between O- electron stimulated desorption (ESD) from hydrogenated and bare polycrystalline diamond films exposed to thermally activated oxygen for incident electron energies in the 4-23 eV range and vibrational electron energy losses. By utilizing the previously established mechanism of low energy ESD of O- from diamond surfaces and high resolution electron energy loss spectroscopy carried out at an incident energy below the threshold for ion desorption, the surface bonding configuration of oxygen is discussed. Such analysis reveals formation of C=O and C-O-C bonds on the bare diamond surface, as well as some adsorbed CO molecules. The bonding configuration of the hydrogenated surface before and after exposure to oxygen is found to be dependent on the hydrogenation method: ex situ microwave plasma versus in situ treatment using a hot tungsten filament for gas activation. Oxygen-related features on the ex situ hydrogenated surface are attributed to formation of C=O and C-O-H bonds, whereas in situ hydrogen treatment retains some bare parts on the film surface where C-O-C bonds can be found alongside C=O and C-O-H. (C) 2003 American Institute of Physics.