title: Electron Momentum Spectroscopy Investigation of Molecular Conformations of Ethanol Considering Vibrational Effects.
abstract: The interpretation of experimental electron momentum distributions (EMDs) of ethanol, one of the simplest molecules having conformers, has confused researchers for years. High-level calculations of Dyson orbital EMDs by thermally averaging the gauche and trans conformers as well as molecular dynamical simulations failed to quantitatively reproduce the experiments for some of the outer valence orbitals. In this work, the valence shell electron binding energy spectrum and EMDs of ethanol are revisited by the high-sensitivity electron momentum spectrometer employing symmetric noncoplanar geometry at an incident energy of 1200 eV plus binding energy, together with a detailed analysis of the influence of vibrational motions on the EMDs for the two conformers employing a harmonic analytical quantum mechanical (HAQM) approach by taking into account all of the vibrational modes. The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively, indicating that the vibrational effect plays a significant role in reproducing the experimental results, not only through the low-frequency OH and CH3torsion modes but also through other high-frequency ones. Rational explanation of experimental momentum profiles provides solid evidence that the trans conformer is slightly more stable than the gauche conformer, in accordance with thermodynamic predictions and other experiments. The case of ethanol demonstrates the significance of considering vibrational effects when performing a conformational study on flexible molecules using electron momentum spectroscopy.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Yaguo
authors.identifier: http://orcid.org/0000-0003-4255-7774
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Shan
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Niu
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Enliang
authors.initials: E
authors.lastname: Wang
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai 980-8577, Japan.
authors.forename: Noboru
authors.initials: N
authors.lastname: Watanabe
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai 980-8577, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yamazaki
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai 980-8577, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Xiangjun
authors.identifier: http://orcid.org/0000-0002-4354-9330
authors.initials: X
authors.lastname: Chen