It has been shown by a series of photometric readings on thirty spark lines of mercury falling in the range 2000-5000 angstroms, that these lines fall into three groups. (1) Excitation potential at about 20 volts, (2) excitation potential about 28 volts and (3) excitation potential about 55 volts. The exact values of these potentials are uncertain since they depend upon pressure and current conditions. If we accept the results of Smythe that double ionization occurs first at 20 volts and triple ionization certainly not under 100 volts we may suppose the first class of lines as due to the removal of the second valence electron. The other lines are not so easily explained but are probably due to electrons displaced from the inner levels.
Proceedings of the Iowa Academy of Science
©1926 Iowa Academy of Science, Inc.
Eldridge, J. A.
"Potentials of Spark Lines of Mercury vapor,"
Proceedings of the Iowa Academy of Science, 33(1), 249-249.
Available at: https://scholarworks.uni.edu/pias/vol33/iss1/68