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 N-2. Analysis of experimental spectra reveals that the 1 sigma(g) and 1 sigma(u) core-hole states differ in energy by similar to 100 meV and in equilibrium bond length by similar to 0.04 pm, in agreement with ab initio predictions. The ratio of the 1 sigma(g) and 1 sigma(u) 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 1 sigma(g) and 1 sigma(u) 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.