Core level photoelectron spectroscopy of molecules: resonance, quantum interference, nonadiabatic effect and determination of the geometry of core ionized state

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(1) For small molecules such as N_2, C_2H_2, C0_2, NO, and N_2O, we have elucidated influence of the shape resonance onto the vibrational population of core level photoelectron spectra by measuring them as a function of photon energies and comparing them with ab initio calculations.(2) We have obtained equilibrium geometry of the core ionized states in CO, N_2, CO_2, N_2O, BF_3, and CF_4 from the vibrational population of core-level photoelectron spectra that were not influenced by the shape resonances.(3) We have elucidated quantum interference effect (Young's double slit interference) and the influence of the photoelectron intramolecular elastic scattering and photoelectron recoil onto the double slit interference pattern by measuring the core-level photoelectron emission from N_2 by resolving gerade and ungerade core levels with the energy splitting of 100 meV.(4) We have established high-resolution electron-ion coincidence momentum imaging techniques as well as projection methods for the analysis of the coincidence data. Using these methods, we have obtained core-level photoelectron angular distributions in molecular frame (MF-PADs) for CO_2, NO, CF_4, N_2O and compared them with ab initio calculations. We have elucidated the influence of the shape resonance to the MF-PADs, dynamical core-hole localizations, validity of the two-step model, as well as intramolecular inelastic electron scattering as a mechanism for the formation of the photoelectron satellites.