Potential energy diagram for hydrogen near vanadium surface

In order to examine the mechanism of the hydrogen recombination phenomenon, the potential energy diagram for hydrogen isotopes near a vanadium surface was experimentally studied. One side of a sample membrane was continuously exposed to deuterium plasma and the surface density and the bulk concentration of deuterium were measured by nuclear reaction analysis. At the same time, the permeation flux to the other side was monitored. The recombination coefficient on the plasma-exposed surface agreed well with the theoretical value for a clean surface. The activation energies for the recombination process and the jump process from the surface to the bulk were found to be 0.23 and 0.04 eV, respectively. There is a barrier potential of 0.29 eV on the vacuum-facing surface, which can be attributed to surface impurities.