Studies of the ionization of molecules by electron impact I. Excited states of the nitrogen molecular ion

Abstract A recently developed pulse technique which produces a beam of electrons with an energy spread of only 0·1 eV has been used to determine the ionization efficiency curve for molecular nitrogen in a mass spectrometer. Ionization to all four known excited states of the N+2 ion, including the recently identified 2π u state, are clearly recognizable on the ionization efficiency curve. The several ionization potentials of the nitrogen molecule, as given by this new electron impact method, are in good agreement with the values deduced from spectroscopic data. The results are also shown to be in agreement with the expectations of the molecular orbital formula for nitrogen given some years ago by Mulliken (1932).