Helium Atom Scattering from Cold Salty Water: Impact of Microscopic and Mesoscopic Surface Structure
8 affiliations
- 1Department of Chemistry
- 2University of California
- 3Chemical Sciences Division
- 4Lawrence Berkeley National Laboratory
- 5School of Chemistry and Chemical Engineering and Chongqing Key Laboratory of Chemical Theory and Mechanism
- 6Chongqing University
- 7Center for Computational Chemistry
- 8University of New Mexico
Abstract
Understanding the dynamics of gas–liquid surface scattering is of fundamental importance to interfacial phenomena ranging from atmospheric chemistry to heterogeneous catalysis. In this work, molecular beam scattering experiments and all-atom molecular dynamics (MD) simulations are carried out to study collisions of He atoms ( E i = 5.8 kJ mol −1 ; θ i = 45°, 60°, and 75°) from the surface of a cold salty water (8 m LiBr (aq) , 230 K) flat jet. The measured translational energy distributions are collected as a function of the scattering angle in the same plane of the incidence beam and indicate dominant impulsive scattering with little to no trapping–desorption signal. The fractional energy loss values are small and nearly invariant across a wide range of deflection angles. MD simulations with fine-tuned force field parameters reproduce the experimental energy transfer reasonably well, providing insight into the collision dynamics at the microscopic level. However, the highly diffuse experimental angular distributions with significant intensities in the direction parallel to the liquid surface ( θ f = 90°) are in sharp contrast to the narrower and near specular angular distributions in simulations. This theory–experiment discrepancy is attributed to capillary and mechanical waves of the liquid surface and much better agreement between theory and experiment for He scattering is achieved by invoking a mesoscopic washboard model. This model also successfully reproduces previously reported results for Ne at E i = 24.3 kJ mol −1 . Our combined experimental–computational approach establishes that microscopic collision dynamics and mesoscopic surface morphology jointly govern scattering from salty water surfaces, providing a framework for interpreting and predicting interfacial energy transfer in complex liquid environments.
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BibTeX
@misc{yang2026helium,
title = {{Helium Atom Scattering from Cold Salty Water: Impact of Microscopic and Mesoscopic Surface Structure}},
author = {Walt Yang and Junhong Li and Madison M. Foreman and Tiffany C. Ly and Hua Guo and Jun Li and Daniel M. Neumark},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010915/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010915/v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Helium Atom Scattering from Cold Salty Water: Impact of Microscopic and Mesoscopic Surface Structure
AU - Walt Yang
AU - Junhong Li
AU - Madison M. Foreman
AU - Tiffany C. Ly
AU - Hua Guo
AU - Jun Li
AU - Daniel M. Neumark
PY - 2026
DA - 2026/10/22
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010915/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010915/v1
AB - Understanding the dynamics of gas–liquid surface scattering is of fundamental importance to interfacial phenomena ranging from atmospheric chemistry to heterogeneous catalysis. In this work, molecular beam scattering experiments and all-atom molecular dynamics (MD) simulations are carried out to study collisions of He atoms ( E i = 5.8 kJ mol −1 ; θ i = 45°, 60°, and 75°) from the surface of a cold salty water (8 m LiBr (aq) , 230 K) flat jet. The measured translational energy distributions are collected as a function of the scattering angle in the same plane of the incidence beam and indicate dominant impulsive scattering with little to no trapping–desorption signal. The fractional energy loss values are small and nearly invariant across a wide range of deflection angles. MD simulations with fine-tuned force field parameters reproduce the experimental energy transfer reasonably well, providing insight into the collision dynamics at the microscopic level. However, the highly diffuse experimental angular distributions with significant intensities in the direction parallel to the liquid surface ( θ f = 90°) are in sharp contrast to the narrower and near specular angular distributions in simulations. This theory–experiment discrepancy is attributed to capillary and mechanical waves of the liquid surface and much better agreement between theory and experiment for He scattering is achieved by invoking a mesoscopic washboard model. This model also successfully reproduces previously reported results for Ne at E i = 24.3 kJ mol −1 . Our combined experimental–computational approach establishes that microscopic collision dynamics and mesoscopic surface morphology jointly govern scattering from salty water surfaces, providing a framework for interpreting and predicting interfacial energy transfer in complex liquid environments.
ER -