Interaction of gaseous H atoms with Cu(100) surfaces: adsorption, absorption, and abstraction

The interaction of H atoms with clean and D-covered Cu(100) surfaces was st udied with LEED, TPD and direct product detection methods. H(D) exposure of Cu(100) surfaces leads to a p(2 x 2) reconstruction and adsorbed and absor bed species. Absorbed H(D) desorbs via recombination between 150 and 200 It according to a zero order rate law with 0.35 eV activation energy. Adsorbe d species desorb via second order between 200 and 350 K. Abstraction of D b y gaseous H at 80 K leads to HD and D, formation, with 1% of the adsorbed D occurring in homonuclear products. These and the HD kinetics contradict th e operation of an Eley-Rideal mechanism, but are in accordance with the ope ration of a hot-atom mechanism. Absorbed D is not abstracted. The D abstrac tion kinetics exhibit significant differences from that measured on Cu(111) surfaces and suggest that abstraction is sensitive to the surface structur e of a substrate. (C) 2000 Elsevier Science B.V. All rights reserved.