Heterogeneous ice nucleation and growth on small nanoparticles heated up by light absorption

Heterogeneous ice nucleation on sub-2nm meteor smoke particles (MSP) plays an important role on the cloud formation in the mesopause region of Earth at heights of 80-90 km. Noctilucent clouds (NLC) in this region have attracted much attention as a peculiar phenomenon observed only during the polar summer. However, very little is known about the physicochemical formation process of NLC so far. An experimental system is required to clarify the nucleation and growth process on MSPs under realistic mesopause conditions. The TRAPS apparatus at KIT is used to investigate the heterogeneous nucleation process on MSPs by observing the mass growth rate of nanoparticles trapped under controlled H2O temperature and pressure with a time-of-flight mass spectrometer. We have recently developed an additional experimental system allowing us to expose the trapped nanoparticles to laser irradiation to study the heat-up behavior of MSPs by solar light absorption during the polar summer. In this study we compare the amount of adsorbed water molecules on the MSP analogues with and without laser irradiation of different input powers to infer the heat up of the particles and determine their absorption cross section. ... mehrIn addition, we discuss how temperature changes of the nanoparticles affect the ice nucleation and growth process.