The influence of a thin gold film on vibrational excitation of hydrogen molecules

The vibrational populations have been measured for hydrogen molecules issuing from a cell containing a mixture of atomic and molecular hydrogen in the presence of an incandescent tungsten filament. The cell walls were covered with a gold film by in situ evaporation. The gold film was observed to exist in two forms, the first being transformed irreversibly into the second by annealing. The observed behavior of the vibrational populations differed from those observed previously with other metals in that the relative distributions depended on the filament temperature. This behavior was interpreted as being the result of either special characteristics of the hydrogen–tungsten interaction at the filament or the presence of a potential barrier in the reaction path for the formation of hydrogen molecules by the process of recombinative desorption.