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Updated: Jan 16, 2026
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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
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Absorption and Scattering Properties of Atmospheric Molecular Clusters.
Georg Baadsgaard Trolle1, Jakub Kubečka1, Jonas Elm1
1Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.
The Journal of Physical Chemistry. A
|September 26, 2025
Summary
This study uses quantum chemistry to explore the optical properties of atmospheric molecular clusters. Larger clusters show increased Rayleigh scattering, but their short lifetimes limit greenhouse gas potential.
Area of Science:
- Atmospheric Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Optical properties of atmospheric molecular clusters are poorly understood due to experimental challenges.
- Acid-base molecular clusters play a role in atmospheric processes.
Purpose of the Study:
- To investigate the absorption and Rayleigh scattering properties of various acid-base molecular clusters.
- To determine the effect of cluster size and composition on optical characteristics.
Main Methods:
- Quantum chemical calculations (CAM-B3LYP/aug-cc-pVTZ) were employed.
- Polarizability tensors and excitation energies were computed for small and large cluster systems.
- Studied 127 small (acid)1-2(base)1-2 clusters and large (sulfuric acid)n(ammonia)n clusters (n up to 15).
Main Results:
- Isotropic polarizability scales nearly linearly with cluster size.
- Anisotropic polarizability plateaus with increasing cluster size.
- Rayleigh scattering activity increases quadratically with cluster size due to dominant isotropic contribution.
Conclusions:
- Cluster size significantly influences Rayleigh scattering, with larger clusters exhibiting stronger scattering.
- Acid-base clusters absorb IR radiation but are unlikely to be significant greenhouse gases due to short lifetimes.
- UV-vis absorption occurs in the deep UV; future studies should focus on clusters with higher organic content.
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