Direct observations of the chemical shift and electron momentum distributions of core shell in N2O

Combining a theoretical and experimental investigation of electron momentum spectroscopy (EMS) of the N 1s hole (2σ−1 and 3σ−1) orbitals in NNO (X 1Σ+), we demonstrate a direct and pronounced manifestation of a chemical shift of the molecule. Evidence from both binding-energy spectra and the corresponding orbital momentum distributions are presented for the chemical shift of 3.4 eV in ionization energy and differences of wave functions of NNO between the terminal N (3σ−1 NT) and center N (2σ−1 NC).