Probing the shape and stereochemistry of molecular orbitals in locally flexible aromatic chains: A penning ionization electron spectroscopy and Green's function study of the electronic structure of biphenyl

Naoki Kishimoto, Yusuke Hagihara, Koichi Ohno, Stefan Knippenberg, Jean Pierre François, Michael S. Deleuze

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

We report on the results of an exhaustive study of the interplay between the valence electronic structure, the topology and reactivity of orbitals, and the molecular structure of biphenyl by means of Penning ionization electron spectroscopy in the gas phase upon collision with metastable He*(2 3S) atoms. The measurements are compared with one-particle Green's function calculations of one-electron and shake-up valence ionization spectra employing the third-order algebraic diagrammatic construction scheme [ADC(3)]. Penning ionization intensities are also analyzed by means of the exterior electron-density model and comparison with photoelectron spectra: in contrast with the lines originating from a orbitals, ionization lines belonging to the π-band system have large Penning ionization cross sections due to their greater extent outside the molecular van der Waals surface. The involved chemi-ionization processes are further experimentally investigated using collision-energy-resolved Penning ionization electron spectroscopy. The cross sections of π-ionization bands exhibit a markedly negative collision-energy dependence and indicate that the interaction potential that prevails between the molecule and the He*(23S) atom is strongly attractive in the π-orbital region. On the other hand, the partial ionization cross sections pertaining to σ-ionization channels are characterized by more limited collision-energy dependencies, as a consequence of rather repulsive interactions within the σ-orbital region. A comparison of ADC(3) simulations with the Penning ionization electron spectra and UV photoelectron spectra measured by Kubota et al. [Chem. Phys. Lett. 1980, 74, 409] on thin films of biphenyl deposited at 170 and 109 K on copper demonstrates that biphenyl molecules lying at the surface of polycrystalline layers adopt predominantly a planar configuration, whereas within an amorphous sample most molecules have twisted structures similar to those prevailing in the gas phase.

Original languageEnglish
Pages (from-to)10535-10546
Number of pages12
JournalJournal of Physical Chemistry A
Volume109
Issue number46
DOIs
Publication statusPublished - 2005 Nov 24

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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