Proton-Coupled Electron Transfer in a Quantum Solvent

Superfluid helium nanodroplets have recently demonstrated their capabilities as nano-cryostats for the real-time investigation of light-matter interaction processes in novel molecular systems and clusters which so far have eluded observation. Within two previous projects, femtosecond pump- probe spectroscopy of molecules solvated inside He droplets was developed and theoretical approaches for simulation and interpretation of dynamical processes were tested. The current project will build on these achievements and investigate photoinduced intermolecular proton-coupled electron transfer (PCET) in chromophore-solvent clusters located inside He droplets. PCET is a special class of hydrogen transfer processes, which follow an energetically favorable reaction pathway due to their sequential character of electron and proton transfer. We will investigate both PCET reaction directions separately, namely from a photoexcited chromophore to surrounding solvent molecules and vice versa. This approach shall open a new path for time-domain investigations of molecular aggregates, by demonstrating the droplets superiority in terms of cooling and stabilization over other techniques. Furthermore, solvent-to-chromophore PCET shall be completely characterized in the time domain for the first time, with potential relevance for the conversion of solar energy into chemical energy of fuels. The project will be carried out at the Ultrafast Laser Laboratories at the TU Graz Institute of Experimental Physics, in collaboration with researchers from University of Toulouse, France.