The observation of electric-dipole-forbidden inner-shell transitions in N₂ and Ar by the electron energy-loss technique

By using low-energy electron impact excitation the authors have observed the first example of an inner-shell single-to-triplet transition, namely the transition from the ground state to the (1s)^-1( pi 2p) ³ Pi state of N₂. The parameters omega _e and R_e of the triplet state have been deduced from the observed vibrational structure of the transition. The parity-forbidden transition to the (2p₃2/)^-14p state of Ar has also been studied, and the intensity of this transition relative to that of the electric-dipole-allowed transition to the (2p₃2/)^-14s state has been measured as a function of the incident electron energy.