Alumni-Preis 2025
Leonie Katharina Werner für ihre Masterarbeit: "A novel action-detection scheme for wave packet interferometry of organic molecules in helium nanodroplets"
Leonie Werner
Betreuer: PD Dr. Lukas Bruder
Abstract of thesis:
A large proportion of photochemical processes in organic molecules happen non-radiatively, hence, it is of particular interest to develop experimental techniques that enable their investigation. Photoelectron spectroscopy is well-suited for probing non-radiative transitions. However, to date, the majority of photoelectron spectroscopy is conducted in the gas phase. Thus, the influence of an environment on the molecular dynamics is not considered. Embedding the molecule in helium nanodroplets enables the investigation of interaction dynamics between the dopant and the droplet. Helium nanodroplets act as a weakly-perturbing testbed to investigate single molecules in the gas phase. In this work, time-resolved photoelectron experiments have been conducted with the organic molecules tetracene and the prototypical photoswitch azobenzene exploiting helium nanodroplet isolation. An increase of low kinetic energy photoelectron yield is observed for both systems upon photoexcitation that induces non-radiative transitions. Evaluation of the droplet size-dependent dynamics yields the conclusion that two processes are taking place. A superposition of helium evaporation and dopant ejection is causing the increase of low kinetic energy photoelectron yield upon excitation, due to fewer interactions with the helium environment. First measurements of utilizing the change in photoelectron signal of azobenzene-doped helium nanodroplets for wave packet interferometric measurements are feasible. Excitation spectra show broad features that can not be distinguished from the excitation laser spectrum. This points to the fact that with the chosen pump wavelength range oligomers are predominantly excited.