Speaker:
Jozef Lengyel
Technical University of Munich, School of Natural Sciences, Lichtenbergstr. 4, 85748 Garching, Germany
Abstract:
Aerosol particles represent one of the most important, yet perhaps the least understood, components of our atmosphere. Small particles have long been recognized in numerous atmospheric processes, providing a playground for heterogeneous chemistry. To investigate these processes in laboratory experiments, we employ free clusters—(sub)nanometer-sized particles—in molecular and ion beams. These offer two key benefits: (1) the use of mass spectrometry, providing precise information about the cluster's composition, and (2) keeping an environment free of external influences, such as substrates and solvents. Precise control of the cluster composition then enables us to build up particles with the desired composition, facilitating the investigation of these effects and other size-dependent properties. Three recent case studies will be presented. In the first one, I will talk about the dynamics of collisions and the uptake of molecules by mixed HNO3/H2O clusters. Our molecular beam experiment, which combines cluster mass spectrometry with velocity measurements, enables us to determine sticking efficiencies. In the second one, I will focus on the dissociation of nitric acid on large water clusters (ice nanoparticles). Herein, the (H2O)N clusters are doped with a single HNO3 molecule and probed by mass spectrometry after a low-energy electron attachment. Our experiments reveal that upon adsorption on ice nanoparticles, some HNO3 molecules dissociate, yet the majority remain non-dissociated. The final study will illustrate reactivity experiments in our cryogenic ion trap, highlighting a complex, size-dependent chemistry in the coupling of CO2 and CH4.
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Open to all IP2I members, as well as UCBL and CNRS students and collaborators.
More information on seminars: https://intranet.ip2i.in2p3.fr/vie-scientifique/seminaires-ip2i
IP2I agenda: https://www.ip2i.in2p3.fr/agendav2/
