New Evidence Regarding the Interpretation of Critical Potentials in Hydrogen

Abstract

Critical Potentials in Hydrogen.—(1) Experimental separation of effects due to atomic and molecular hydrogen. In an ionization tube of the Lenard type, a close grid of tungsten wires was introduced between the filament and the gauze in front of the plate. When this grid was heated electrically to incandescence the proportion of atoms was greatly increased by dissociation of the molecules. (2) Effects due to radiation were distinguished from effects of ionization by comparing the electron currents to a disk electrode with those to a wire which because of its small area was relatively insensitive to effects of radiation. (3) Six critical potentials between 10 and 16 volts were observed and measured with reference to the strongest break, assumed to occur at 16.0 volts. Each break point was located at the intersection of two tangents; hence the relative values are probably accurate to 2 or 3 per cent. Purified electrolytic hydrogen was used. (4) Experimental interpretation of the breaks, which agrees in general with the previous theoretical interpretation based on quantum theory, is as follows: radiation from the atom at 10.1 and at 12.2 volts, corresponding to the first two terms of the Lyman series; ionization of the molecule at 11.5 volts and of the atom at 13.6 volts; dissociation of the molecule and radiation at 12.9 volts; finally, dissociation of the molecule and ionization of one of its parts at 16.0 volts. The energy required for dissociation of the molecule is therefore equivalent to about 2.8 volts.