Adsorption of hydrogen on clean and oxidized beryllium studied by direct recoil spectrometry

Direct monitoring of hydrogen adsorption on clean and on pre-oxidized polycrystalline beryllium by means of direct recoil spectrometry (DRS) is reported. While no adsorption occurs for molecular hydrogen either on clean or on oxidized beryllium, atomic hydrogen adsorbs on the surface of clean Be, as well as at the sites available between oxygen clusters, formed by low oxygen pre-exposure. For higher oxygen pre-exposures, when oxide islands are formed, the apparent coverage of hydrogen is significantly lower than the amount needed for complementary full coverage on the Be surface. Possible origins for this observation are discussed.