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

Few UV photoelectron spectrum bands observed in the closed shell molecules can be rationalized by molecular orbitals possessing spin and spatial degen eracies, which is in accord with the model of an electron-configuration con sisting of electron pairs with doubly occupied orbitals. Numerous UV photoe lectron spectrum bands observed in the open-shell species O-2 and NO needs to be rationalized by molecular orbitals with spin and spatial degeneracies removed; and thus the formal electron-configuration consisting of doubly o ccupied 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. ( C) 2000 Elsevier Science B.V. All rights reserved.