Chemical bonding effect in electron scattering by gaseous molecules

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network 1 , including unusually efficient vibrational energy redistribution and relaxation 2 . An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments 2-7 . However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here we measured the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of ~1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on the femtosecond timescales. Our experiment and simulations unveiled the intermolecular character of the water vibration preceding the relaxation of the OH stretch.The vibrational spectroscopy of water has critically contributed to our understanding of the dynamics of hydrogen bond (HB) reorganization and energy redistribution in liquid water. It is

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“…Ref. 58 ). For the QΔS signal at Q>1 Å -1 , they do not match the characteristic shape of inelastic scattering.…”

Section: Ab Initio Electron Scattering Simulationmentioning

confidence: 99%

Direct observation of ultrafast hydrogen bond strengthening in liquid water

Yang

Dettori

Nunes

et al. 2021

Nature

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“…This has led to the assumption that conventional (independent atom model, IAM) HRTEM image simulation is sufficient for structural and elemental identification. The effect of binding electrons has been detected experimentally in electron diffraction experiments [7,8], but so far was not discerned in TEM images. However, diffraction experiments are limited to periodic structures and sufficiently large samples.…”

Section: Introductionmentioning

confidence: 99%

Charged defects in graphene and the ionicity of hexagonal boron nitride in direct images

Meyer¹,

Kurasch²,

Park³

et al. 2010

Preprint

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We report on the detection and charge distribution analysis for nitrogen substitutional dopants in single layer graphene membranes by aberration-corrected high-resolution transmission electron microscopy (HRTEM). Further, we show that the ionicity of single-layer hexagonal boron nitride can be confirmed from direct images. For the first time, we demonstrate by a combination of HRTEM experiments and firstprinciples electronic structure calculations that adjustments to the atomic potentials due to chemical bonding can be discerned in HRTEM images. Our experiments open a way to investigate electronic configurations in point defects or other non-periodic arrangements or nanoscale objects that can not be studied by an electron or x-ray diffraction experiment.

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“…A chemical bonding effect has been observed in the electron scattering signal of molecules in the gas phase, observed mainly at small scattering angles (Iijima et al, 1965;Fink & Kessler, 1967;Duguet & Jaegle, 1975;Hirota et al, 1981;An-Ding & Xiao-Lei, 1995). This has been theoretically studied to quantify the effect in a number of molecules (Bonham & Iijima, 1963;Wang et al, 1994;Hoffmeyer et al, 1998;Shibata et al, 1999Shibata et al, , 2002. We discuss this effect in the total X-ray and electron scattering of gas-phase molecules, further quantifying the error that occurs in the structure determination, and proposing an approach to separate out the molecular structure contribution in the signal from the contribution from the electronic structure.…”

Section: Background On Gas-phase X-ray and Electron Scatteringmentioning

confidence: 99%

“…The peak percent differences for CHD and naphthalene are relatively large, with %�Iðq ¼ 2:4Þ = À 9.6% and %�Iðq ¼ 2:7Þ = À 8.6%, respectively. They are pure hydrocarbons which have been reported to contain larger chemical bonding effects compared with molecules such as CCl 4 , N 2 , O 2 and CS 2 (Shibata et al, 2002). This is due to delocalization of electrons by chemical bonding, which the IAM does not take into account, including double and triple bonds, aromatic rings, and hydrogen atoms bonded to heavier atoms.…”

Section: Iam and Ab Initio Scattering Calculationsmentioning

confidence: 99%

Extracting the electronic structure signal from X-ray and electron scattering in the gas phase

Northey,

Kirrander,

Weber

2024

J Synchrotron Rad

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X-ray and electron scattering from free gas-phase molecules is examined using the independent atom model (IAM) and ab initio electronic structure calculations. The IAM describes the effect of the molecular geometry on the scattering, but does not account for the redistribution of valence electrons due to, for instance, chemical bonding. By examining the total, i.e. energy-integrated, scattering from three molecules, fluoroform (CHF3), 1,3-cyclohexadiene (C6H8) and naphthalene (C10H8), the effect of electron redistribution is found to predominantly reside at small-to-medium values of the momentum transfer (q ≤ 8 Å−1) in the scattering signal, with a maximum percent difference contribution at 2 ≤ q ≤ 3 Å−1. A procedure to determine the molecular geometry from the large-q scattering is demonstrated, making it possible to more clearly identify the deviation of the scattering from the IAM approximation at small and intermediate q and to provide a measure of the effect of valence electronic structure on the scattering signal.

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Chemical bonding effect in electron scattering by gaseous molecules

Cited by 5 publications

References 10 publications

Direct observation of ultrafast hydrogen bond strengthening in liquid water

Direct observation of ultrafast hydrogen bond strengthening in liquid water

Charged defects in graphene and the ionicity of hexagonal boron nitride in direct images

Extracting the electronic structure signal from X-ray and electron scattering in the gas phase

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