The split of the electron pairs and the UV photoelectron spectra of open-shell species

Abstract

Few UV photoelectron spectrum bands observed in the closed shell molecules can be rationalized by molecular orbitals possessing spin and spatial degeneracies, which is in accord with the model of an electron-configuration consisting of electron pairs with doubly occupied orbitals. Numerous UV photoelectron spectrum bands observed in the open-shell species O2 and NO needs to be rationalized by molecular orbitals with spin and spatial degeneracies removed; and thus the formal electron-configuration consisting of doubly occupied orbitals become ambiguous because the electron pairs are split. The electron-pair split not only accounts for the number of the bands observed, but it also accounts for different properties and bonding natures within the ions resulted from ejecting an electron from the open-shell molecule.