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Title: The band 12 issue in the electron momentum spectra of norbornane: A comparison with additional Green's Function calculations and ultraviolet photoemission measurements
Authors: KNIPPENBERG, Stefan
DELEUZE, Michael
CLEIJ, Thomas
FRANCOIS, Jean-Pierre
Cederbaum, LS
Eland, JHD
Issue Date: 2005
Citation: JOURNAL OF PHYSICAL CHEMISTRY A, 109(19). p. 4267-4273
Abstract: In continuation of a recent study of the electronic structure of norbornane [J. Chem. Phys., 2004, 121, 10525] by means of electron momentum spectroscopy (EMS), we present Green's Function calculations of the ionization spectrum of this compound at the ADC(3) level using basis sets of varying quality, along with accurate evaluations at the CCSD(T) level of the vertical (26.5 eV) and adiabatic (22.1 eV) double ionization thresholds under C-2v symmetry. The obtained results are compared with newly recorded ultraviolet photoemission spectra (UPS), up to binding energies of 40 eV. The theoretical predictions are entirely consistent with experiment and indicate that, in a vertical depiction of ionization, shake-up states at binding energies larger than ∼ 26.5 eV tend to decay via emission of a second electron in the continuum. A band of s-type symmetry that has been previously seen at ∼ 25 eV in the electron impact ionization spectra of norbornane is entirely missing in the UPS measurements and theoretical ADC(3) spectra. With regard to these results and to the time scales characterizing electron-electron interactions in EMS (10(-17) s) as compared with that (10(-13) s) of photon-electron interactions in UPS, and considering the p-type symmetry of the electron momentum distributions for the nearest 1b(1) and 1b(2) orbitals, this additional band can certainly not be due to adiabatic double ionization processes starting from the ground electronic state of norbornane, or to exceptionally strong vibronic coupling interactions between cationic states derived from ionization of the latter orbitals. It is therefore tentatively ascribed to autoionization processes via electronically excited and possibly dissociating states.
Notes: Limburgs Univ Ctr, Dept SBG, B-3590 Diepenbeek, Belgium. Univ Heidelberg, Inst Phys Chem, D-69120 Heidelberg, Germany.Deleuze, MS, Limburgs Univ Ctr, Dept SBG, Univ Campus, B-3590 Diepenbeek, Belgium.deleuze@luc.ac.be
URI: http://hdl.handle.net/1942/2166
DOI: 10.1021/jp044130w
ISI #: 000229134300009
ISSN: 1089-5639
Category: A1
Type: Journal Contribution
Validation: ecoom, 2006
Appears in Collections: Research publications

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