Attempts to Observe an Electron Affinity Spectrum

The failure of previous attempts to observe an electron affinity spectrum (emitted by the combination of neutral, electronegative atoms and electrons) is explained by inadequate experimental methods. On the basis of recent results regarding combination spectra of positive ions and electrons, new attempts have been made to observe the electron affinity spectrum of atomic iodine by using three methods (hollow cathode, positive column with addition of a rare gas, glowing filament). No new spectrum was observed. This failure is discussed theoretically. It seems that the capture of electrons by halogen atoms is an improbable process as compared with the combination of positive ions and electrons.