Synthesis of Bulk H in Ni

While the dissolution of gases into the bulk of metals is pervasive and has long been studied using classical techniques, observation of the same in UHV surface environments has been stymied. Specifically, dissolution often is not observed at low H2 pressures because the dissociative absorption is activated and/or endothermic, such as in the case of H2 on Ni(111). We have demonstrated that hydrogen absorption into the bulk of Ni can be overcome by exposure to atomic H (Phys. Rev. Lett. 67, 927 (1991)). As much as an equivalent of ten monolayers can be absorbed. The bulk H can be removed from the metal by raising the temperature to 180-220K. We would like to study the mechanism and dynamics of this unique recombination step by measuring the energy distribution of the H2 desorbing by a resonance enhanced multiphoton ionization scheme.