ニッケル表面に吸着された気体分子に電子衝撃を与えた発生する気体の研究

抄録

A piece of nickel plate on which surface ammonia gas was adsorbed is bombarded by slow electrons and the process of gas evolution is studied by analysis, the principle of the method of which is based upon Knudsen's equation expressing that the flow of low pressure gas through a narrow tube is inversely proportional to the square root of molecular weight of the gas. The adsorbed gas being ammonia, exact analysis becomes possible because of condensation of ammonia at liquid air temperature. By this condensation, proportion of hydrogen, if any, in the evolved gas can be made known by pressure measurements.
Three different processes of gas evolution were observed, (1) When the electron energy is below 6 volts, ammonia evolves undecomposed. (2) At 6 volts, decomposition of ammonia suddenly begins-probably by bimolecular reaction-and hydrogen evolves. The evolution has its peak at 12 volts. (3) From about 16 volts, another kind of decomposition-by monomolecular reaction-begins, the product increasing monotonously as the energy of electrons is raised.
Next, the case of adsorption of water vapour was examined. The spoiling action of water vapour on cathode reduced the electron current, hence the amount of evolved gas, very much, rendering the measurement almost impracticable. A device was made to cope with this case by the use of two cathodes, oxide cathode and pure tungsten cathode. When decomposed, water vapour gives measurable permanent gases; this made the determination of the amount of evolved water vapour possible by observing the difference in amounts of decomposed products on the two cathodes. The obtained results itemized below are more or less the same as in the case of ammonia. (1) When the adsorbed amount is large, water vapour evolves undecomposed at low voltages of approximately 3 volts. (2) At 7 volts, water vapour decomposes suddenly by bimolecular reaction and hydrogen evolves. The evolution has its peak at 12 volts. (3) From 16 volts, the decomposition is by a different process, the monomolecular reaction, the product increasing remarkably with the rise of voltage.