AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Determining the Proton Affinity of Atmospheric Molecular Ions
KAI RUUSUVUORI, Theo Kurten, Ismael Kenneth Ortega Colomer, Hanna Vehkamäki, University of Helsinki
Abstract Number: 115 Working Group: Aerosol Physics
Abstract Understanding the birth and interaction mechanisms of atmospheric aerosols is essential if we are to understand e.g. climate change and the health effects of aerosols. While the role of ion-induced nucleation is not believed to be dominant in the atmosphere (Kulmala et al., 2007), understanding the role of charge in the first steps of nucleation is important.
Proton affinity describes the ability of a molecule to accept a proton and is an important thermodynamic quantity. However, absolute gas-phase proton affinities are hard to measure, which makes theoretical methods a valuable tool in determining these absolute values. Our aim is to study the absolute values of proton affinities using quantum chemical methods. These methods will be applied to several positively charged molecular ion species that have been observed by Ehn et al. (2010).
Based on benchmarking calculations using several different quantum chemical methods, the CBS-QB3 method was chosen for the proton affinity calculations. Calculations have been performed using Gaussian 09 and the obtained values have been compared to results listed in the National Institute of Standards and Technology (NIST) database when possible. Intermediate results show good agreement with NIST values.