Multi-collisional conditions in ion traps as a novel tool towards a molecular understanding of atmospheric aerosol nucleation

• Applicant: Dr. Jozef Lengyel
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 442679477

Aerosols play a crucial role in atmospheric chemistry and cloud formation, having a pronounced effect on global climate. They also represent a source of air pollution with a strong impact on human health. Revealing mechanisms of the new particle formation (NPF) and identifying the major chemical compositions, spatial distributions and sources of atmospheric aerosols are, therefore, key requirements for parametrization of aerosol dynamics models to further improve our understanding of aerosol effects on weather, climate and air quality, and to aid interpretation of field measurements. In contrast to aerosol chamber and flow tube experiments, addressing the role of macroscopic parameters in NPF (e.g. saturated vapor pressure), the present project focuses on the molecular level picture of NPF. It aims at the development of an innovative instrument for studying mass-selected hydrated cluster ions in order to unveil the complex ion-induced nucleation at the early stages of atmospheric NPF. This will reveal specific size, structural and compositional motifs and exhibit unique dynamical characteristics. A major innovative contribution consists in the combination of ion traps and multi-collision regimes that enables investigation of the NPF close to ambient conditions. The complex nucleation mechanism will be studied using kinetic modeling in different size regimes, from single molecular ions to hydrated cluster ions from one to hundreds of water molecules. To reach these conditions, a setup will be developed, which combines nanoelectrospray, generating small hydrated clusters with tens of water molecules, with an aerodynamic lens in order to considerably increase the degree of hydration up to hundreds of water molecules. The research will concentrate on elementary steps in the NPF studied under well-defined multi-collision conditions with precise control of concentration, pressure and temperature. Since cluster ions under these conditions are constantly thermalized via collision with buffer gas, the temperature-dependent measurements will be performed by cooling/heating of the ion trap in order to determine activation barriers for nucleation. Applying nanocalorimetry, the experiments will also provide specific information about thermochemistry of intracluster reactions, e.g. acid-base mechanisms, responsible for enhanced nucleation rates. The combination of these different approaches within one instrument will provide a comprehensive understanding of the NPF at a molecular scale.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Orthogonal Extraction Reflectron Time-of-Flight Spectrometer ; Quadrupole Mass Filter
• Instrumentation Group: 1720 Spezielle Massenspektrometer (Flugzeit-, Cyclotronresonanz-, Ionensonden, SIMS, außer 306)