Inner valence molecular orbitals and the structure of X-ray photoelectron spectra

X-Ray photoelectron spectroscopy (XPS) and theoretical calculations show that under certain conditions inner valence molecular orbitals (IVMOs) can form within a rather broad binding energy range (15 eV to 50 eV) in compounds of many elements of the Periodic Table. This results in the appearance of a fine structure in their X-ray photoelectron spectra. The structure of X-ray photoelectron spectra associated with electrons of IVMOs correlates with contributions of the filled atomic orbitals (AOs) to the IVMO formation and the structure of compounds. In certain cases, the total contribution of electrons of the inner valence molecular orbitals to the bond energy in molecules and compounds is comparable to that of electrons of the outer valence molecular orbitals. This phenomenon is extremely important and new in principle for chemistry. The bibliography includes 128 references.