Doc. Dominik Heger: Water Ices and Frozen Aqueous Solutions Characterized by Spectroscopies and Microscopy

15th May 2024, 10 AM, J. Heyrovský Institute Brdička Hall

The frozen aqueous solutions are commonly encountered in nature as well as in industrial and laboratory processes. I am interested in characterizing the frozen solutions while focusing on the influence of the cooling rates, impurities present, and sublimation processes. We apply UV-Vis, fluorescence and microscopic techniques that help us to find freezing induced aggregation, acidity changes, and both solutes vitrification and crystallization between the ice crystals. Some ions incorporate into the ice in larger extent than the others, forming electrical potential as large as hundreds of volts (Workman- Reynolds effect). Furthermore, we made steps to simplify the heterogenous environment in the ice matrix by focusing on the photophysics of pure compounds and highly concentrated solutions: we detail the excimers of 1-methylnaphthalene via steady state and ultrafast spectroscopies finding that the Theodor Foerster proposition of their diffusion-controlled formation may not, in general, hold. We also question the widely accepted axiom, that no change in absorption spectrum means no ground state interactions.

About doc. Dominik Heger

I started my career as an organic synthetic chemist, soon finding strong affection for physical chemistry, photochemistry in particular. I have learned the (time-resolved) spectroscopic methods on mechanistic photochemistry, identifying reaction intermediates; later, spectroscopy enabled me to study the ice impurity interactions. My knowledge and skills rest especially in theoretical and applied photophysics, the physics and chemistry of ice.