Breakdown of the One-Electron Picture of Ionization for Hydrocarbon n Systems

The photoelectron spectra of a number of characteristic hydrocarbon n systems are analyzed in terms of Koopmans\u27 and non- Koopmans\u27 contributions within a< limited configuration interaction · (CI) framework. The results for several compounds, including quinodimethanes, fulvenes, annulenes, and related systems, suggest frequent invalidity of the one-electron picture of ionization even in the outer valence region. A similar situation may apply for the corresponding anion spectra, as indicated by the electron transmission spectrum of p-benzoquinone. This and sever a\u27l recent investigations demonstrate a general need for the introduction of a more realistic excited state concept than the one implied by Koopmans\u27 approximation

The Alternant Hydrocarbon Pairing Theorem and All-Valence Electrons Theory. An Approximate LCOAO Theory for the Electronic Absorption and MeD Spectra of Conjugated Organic Compounds. 1.

The significance of the pairing theorem for alternant hydrocarbons is demonstr ated by a variety of experimental data, but standard all-valence electrons methods based on the »Neglect of Differential Overlap« (NDO) approximation fail to predict the observed pairing properties for this class of compounds. In this communication, a new all-valence electrons method is presented, using a basis of L6wdin orthogonalized atomic orbitals. This »Linear Combination of Orthogonalized Atomic Orbitals« (LCOAO) method is designed to predict the electronic absorption and magnetic circular dichroism data for organic :n: systems with particular emphasis on the pairing properties of alternants. Results for phenanthrene and hiphenylene are discussed

Breakdown of the One-Electron Picture of Ionization for Hydrocarbon n Systems

The photoelectron spectra of a number of characteristic hydrocarbon n systems are analyzed in terms of Koopmans\u27 and non- Koopmans\u27 contributions within a< limited configuration interaction · (CI) framework. The results for several compounds, including quinodimethanes, fulvenes, annulenes, and related systems, suggest frequent invalidity of the one-electron picture of ionization even in the outer valence region. A similar situation may apply for the corresponding anion spectra, as indicated by the electron transmission spectrum of p-benzoquinone. This and sever a\u27l recent investigations demonstrate a general need for the introduction of a more realistic excited state concept than the one implied by Koopmans\u27 approximation