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Title: Quantum Chemical Study of Conformational Fingerprints in the Photoelectron Spectra and (e, 2e) Electron Momentum Distributions of n-Hexane
Authors: MORINI, Filippo 
Knippenberg, S.
DELEUZE, Michael 
HAJGATO, Balazs 
Issue Date: 2010
Source: JOURNAL OF PHYSICAL CHEMISTRY A, 114(12). p. 4400-4417
Abstract: The main purpose of the present work is to simulate from many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of n-hexane employing photoelectron spectroscopy (PES) and electron momentum spectroscopy (EMS). This study is based on calculations of the valence ionization spectra and spherically averaged (e, 2e) electron momentum distributions for each known conformer by means of one-particle Green's function [1p-GF] theory along with the third-order algebraic diagrammatic construction [ADC(3)] scheme and using Kohn-Sham orbitals derived from DFT calculations employing the Becke 3-parameters Lee-Yang-Parr (B3LYP) functional as approximations to Dyson orbitals. A first thermostatistical analysis of these spectra and momentum distributions employs recent estimations at the W1h level of conformational energy differences, by Gruzman et al. [J. Phvs. Chem. A 2009, 113, 11974], and of correspondingly obtained conformer weights using MP2 geometrical, vibrational, and rotational data in thermostatistical calculations of partition functions beyond the level of the rigid rotor-harmonic oscillator approximation. Comparison is made with the results of a focal point analysis of these energy differences using this time B3LYP geometries and the corresponding vibrational and rotational partition functions in the thermostatistical analysis. Large differences are observed between these two thermochemical models, especially because of strong variations in the contributions of hindered rolations to relative entropies. In contrast, the individual ionizalion spectra or momentum profiles are almost insensitive to the employed geometry. This study confirms the great sensitivity of valence ionization bands and (e, 2e) momemtum distributions on the molecular conformation and sheds further light on spectral fingerprints of through-space methylenic hyperconjugation, in both PES and EMS experiments.
Notes: Deleuze, MS (reprint author),[Morini, F.; Knippenberg, S.; Deleuze, M. S.; Hajgato, B.] Hasselt Univ, Dept SBG, Grp Theoret Chem & Mol Modelling, B-3590 Diepenbeek, Belgium.
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ISSN: 1089-5639
e-ISSN: 1520-5215
DOI: 10.1021/jp9116358
ISI #: 000275855500047
Category: A1
Type: Journal Contribution
Validations: ecoom 2011
Appears in Collections:Research publications

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