Light interacts differently with small droplets compared with extended condensed matter because of the finite size of these droplets. This also modifies light-induced processes, such as the formation and transport of electrons or chemical reactions. To investigate such phenomena, a novel droplet photoelectron spectrometer with a femtosecond high harmonic laser light source was built, tested and its performance characterized as documented in a series of scientific publications.
Exploiting such finite-size effects enabled us to retrieve accurate information about how slow electrons lose energy and change their direction when they travel through liquid water. Accurate cross sections for low-energy electron scattering in liquid water were made available to the public in a series of scientific publications. Detailed knowledge of electron scattering in water is, for example, crucial for a better understanding of energy dissipation processes that are relevant to radiation chemistry and biology.
The hydrated electron is a species that is supposed to play an important role in the chain of radiation damage processes in biological material. Hence, knowledge of its electronic properties and about its formation upon excitation of aqueous systems by light are important to assess its role in radiation damage. Additionally, the influence of spatial confinement on those properties needs to be assessed. We performed a series of experimental studies, revealing that spatial confinement has no major influence on the electronic properties nor on the relaxation dynamics of the hydrated electron. However, a clear system size dependence was observed for its probability of formation. In the course of our studies, we discovered a previously unknown relaxation process that offers a way to produce slow electrons in a controlled way by excitation with ultraviolet light. All these results have been documented in scientific publication.
Because of the finite size of aerosol particles, sunlight is amplified in their interior. Our investigations have shown that all light-induced reaction steps in atmospheric aerosol particles take place about 3 times faster than in the bulk liquid as a result of the light amplification. Our findings have been published in a scientific article and will have important implications regarding the role of such light induced processes in atmospheric processes.
