High resolution X-ray photoelectron spectroscopy on nitrogen molecules

This paper summarizes recent developments for experimental and theoretical studies on core-level photoelectron spectroscopy of N2. Analysis of experimental spectra reveals that the 1σg and 1σu core-hole states differ in energy by ~100meV and in equilibrium bond length by ~0.04pm, in agreement with ab initio predictions. The ratio of the 1σg and 1σu photoionization cross sections measured in the photon energy range up to 1 keV reveals oscillatory structure due to two-center interference, equivalent to Young’s double-slit experiment, as Cohen and Fano predicted. The experimental Auger rates for the transition to the dicationic ground state are found to be different by a factor of two for 1σg and 1σu hole states and are well reproduced by the ab initio calculations. All these findings support the delocalized picture of the core hole. Discussion is given how many-body processes involved and observations for these processes affect the observation of the localized and/or delocalized core hole.