Experiments on potential energy diagram for hydrogen isotopes on nickel surface

Activation energies for some processes concerned with hydrogen recombinatio n were studied experimentally. One side of a nickel membrane was exposed to a deuterium plasma and the deuterium permeation flux J at a steady state w as monitored. At the same time, the surface density S of deuterium on the p lasma-exposed side was observed by nuclear reaction analysis. The results s howed that both the data of S-2 and J/S fell on straight lines in Arrhenius diagrams. Considering the particle balance equations under the experimenta l conditions, two values of the activation energy for the rate constant wer e obtained: one for two atoms recombining and subsequently leaving from the surface of 0.40 eV and the other for one atom migrating from the surface t o the bulk of 0.57 eV. From these values, the energy term in the convention al form of the recombination coefficient was found to be 0.08 eV. (C) 1999 Elsevier Science B.V. All rights reserved.