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|Title:||Investigation of the molecular conformations of ethanol using electron momentum spectroscopy||Authors:||Ning, C. G.
Luo, Z. H.
|Issue Date:||2008||Publisher:||IOP PUBLISHING LTD||Source:||JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 41(17)||Abstract:||The valence electronic structure and momentum-space electron density distributions of ethanol have been investigated with our newly constructed high-resolution electron momentum spectrometer. The measurements are compared to thermally averaged simulations based on Kohn-Sham (B3LYP) orbital densities as well as one-particle Green's function calculations of ionization spectra and Dyson orbital densities, assuming Boltzmann's statistical distribution of the molecular structure over the two energy minima defining the anti and gauche conformers. One-electron ionization energies and momentum distributions in the outer-valence region were found to be highly dependent upon the molecular conformation. Calculated momentum distributions indeed very sensitively reflect the distortions and topological changes that molecular orbitals undergo due to the internal rotation of the hydroxyl group, and thereby exhibit variations which can be traced experimentally. The B3LYP model Kohn-Sham orbital densities are overall in good agreement with the experimental distributions, and closely resemble benchmark ADC(3) Dyson orbital densities. Both approaches fail to quantitatively reproduce the experimental momentum distributions characterizing the highest occupied molecular orbital. Since electron momentum spectroscopy measurements at various electron impact energies indicate that the plane wave impulse approximation is valid, this discrepancy between theory and experiment is tentatively ascribed to thermal disorder, i.e. large-amplitude and thermally induced dynamical distortions of the molecular structure in the gas phase.||Notes:||Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China. Tsinghua Univ, Key Lab Atom & Mol NanoSci MOE, Beijing 100084, Peoples R China. Hasselt Univ, Dept SBG, Res Grp Theoret Chem, B-3590 Diepenbeek, Belgium.||Document URI:||http://hdl.handle.net/1942/8472||ISSN:||0953-4075||e-ISSN:||1361-6455||DOI:||10.1088/0953-4075/41/17/175103||ISI #:||000258732700006||Category:||A1||Type:||Journal Contribution||Validations:||ecoom 2009|
|Appears in Collections:||Research publications|
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