My main scientific interest relates to studying the formation of new aerosol particles from the gas-phase (nucleation). These newly-formed particles are initially tiny agglomerates of several molecules (diameter of ~1 nm) but they can grow and become efficient cloud condensation nuclei (diameter > 50 nm). Therefore, new particle formation is highly relevant because it affects cloud formation (aerosol-cloud-climate interaction) as well as the atmospheric particle burden, which can lead to adverse health effects.

Measurement of the gas-phase compounds relevant for nucleation (e.g. sulfuric acid, amines, ammonia, and highly oxygenated organic molecules) is challenging due to their minuscule concentrations (1 molecule in 10^12 to 10^14 other molecules). For the measurement of these substances, I apply chemical ionization mass spectrometry, which can also be used to detect neutral nucleating clusters (agglomerates of several molecules). This technique is applied to study new particle formation in a controlled chamber experiment (CLOUD, Cosmics Leaving OUtdoor Droplets experiment at CERN), other laboratory measurements and field experiments. I am also interested in improving the existing instrumental techniques, which includes the application of various primary ions suitable for selective detection of different trace gases. Additionally, my research activities include the development of instrumentation suitable for the chemical analysis of freshly-nucleated particles with sizes between ~5 and 50 nm.