The densities of hydrogen and carbon atoms in a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS) and elastic recoil detection analysis (ERDA). The hydrogen density in DLC decreased upon atomic oxygen beam exposure with collision energy as low as 2 eV, whereas an exposure greater than 3 eV was necessary to remove carbon atoms. A high-collision energy also led to hydrogen desorption in the deeper region of DLC. The surface density of hydrogen decreased 6% by atomic oxygen exposure, and was independent of the collision energy. Additionally, the non-bonded hydrogen, which could diffuse in DLC, was desorbed by the energy transfer from the atomic oxygen collisions. (C) 2009 Elsevier B. V. All rights reserved.