The use of direct recoil spectrometry (DRS) for the study of water vapor interactions on polycrystalline metallic surfaces-the H2O/U and H2O/Ti systems

For the H2O/Ti system, a more complicated mechanism, which involves a precursor state, seems to control the process. In that case, two concurrent routes act simultaneously. In addition to the simple direct-collision mechanism, water precursor clusters (bound by hydrogen bonds), which partly dissociate, result in chemisorbed tilted hydroxyl clusters (even at low-coverage). The relative contributions of the precursor route and the direct-collision route are pressure dependent, with the former being dominant at higher exposure pressures.