Electron Energy Losses in Mercury Vapor

An improved magnetic spectrum method was used to determine the energy losses sustained by slow speed electrons in mercury vapor. Electron energies up to 60 volts were used, the main region of interest being from 0 to 25 volts. The energy losses detected, below that required for ionization, were; 4.9, 5.4, 6.7, 7.7, 8.8, 9.8 volts. These correspond to practically all the transitions of a valence electron from the basic $1S$ level up to each of the higher levels to $4P$. No evidence of other losses such as are observed by the photoelectric method were found. At voltages above 10.4, the ionization potential, electrons seem to be able to give up any quantity of energy in excess of that required for ionization, the higher losses being favored. A very interesting loss of 11.07 volts has been found, which has not been recorded heretofore. It begins to be resolved at about 18 volts, and grows steadily with increasing voltage in much the same manner as the 6.7 volt loss. It is thought that this loss involves the simultaneous displacement of both valence electrons from their normal levels.