Freezing atmospheric organic nucleation clusters

The atmosphere is a highly dynamic place. This is evident not only through the weather and its turbulence and variability but also through the processes that occur on a microscopic level in the air. While air is mostly composed of nitrogen and oxygen, there are also some trace gases in our atmosphere that have a very special property: they stick together well. When one such gas molecule finds another, they adhere to each other and form a molecular cluster. Additional molecules join in, and through this dynamic process, a new particle is created in the air, only about a nanometer in size but with a significant impact: these formed airborne particles, known as aerosols, influence the climate and contribute to air pollution. To better study this dynamic process of aerosol formation, it would be helpful to simply freeze it and then examine it. This is the goal of the new FWF project "Matrix Isolation of Atmospheric Nucleation Clusters" at TU Wien. Atmospheric research has made tremendous progress over the past two decades in understanding aerosol formation, and it has been shown that, in addition to the important sulfuric acid, organic substances can also be crucial for the rapid formation of molecular clusters and hence aerosols. However, most measurement techniques in this field rely on mass spectrometry. While this method can determine the chemical composition of the involved molecules, it cannot measure the details of the chemical bonding processes or unequivocally identify the substances involved. The research team at TU Wien and partners from the University of Vienna now aims to use infrared light to observe the clustering. Although this method is not new, it has never been applied to the subject area of atmospheric aerosol formation because these processes are far too dynamic. Therefore, in the FWF-funded project, the process will be frozen in a noble gas like argon or neon at temperatures close to absolute zero. This approach will investigate the extent to which organic molecules influence the initial aggregation of molecular clusters. Together with theoretical calculations from quantum chemistry, this should lead to a better understanding of aerosol formation. Ultimately, this should provide better answers to questions regarding the role of aerosol formation in climate change and air quality.