Volume 165, 2013

Comparing simulated and experimental molecular cluster distributions

Abstract

Formation of secondary atmospheric aerosol particles starts with gas phase molecules forming small molecular clusters. High-resolution mass spectrometry enables the detection and chemical characterization of electrically charged clusters from the molecular scale upward, whereas the experimental detection of electrically neutral clusters, especially as a chemical composition measurement, down to 1 nm in diameter and beyond still remains challenging. In this work we simulated a set of both electrically neutral and charged small molecular clusters, consisting of sulfuric acid and ammonia molecules, with a dynamic collision and evaporation model. Collision frequencies between the clusters were calculated according to classical kinetics, and evaporation rates were derived from first principles quantum chemical calculations with no fitting parameters. We found a good agreement between the modeled steady-state concentrations of negative cluster ions and experimental results measured with the state-of-the-art Atmospheric Pressure interface Time-Of-Flight mass spectrometer (APi-TOF) in the CLOUD chamber experiments at CERN. The model can be used to interpret experimental results and give information on neutral clusters that cannot be directly measured.

Supplementary files

Article information

Article type
Paper
Submitted
08 Mar 2013
Accepted
15 Apr 2013
First published
16 Apr 2013
This article is Open Access
Creative Commons BY license

Faraday Discuss., 2013,165, 75-89

Comparing simulated and experimental molecular cluster distributions

T. Olenius, S. Schobesberger, O. Kupiainen-Määttä, A. Franchin, H. Junninen, I. K. Ortega, T. Kurtén, V. Loukonen, D. R. Worsnop, M. Kulmala and H. Vehkamäki, Faraday Discuss., 2013, 165, 75 DOI: 10.1039/C3FD00031A

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