Fundamental Dynamics in Molecules, Clusters, and Interfacial Systems Studied with Novel XUV and X-ray Light Sources
Ultrafast XUV and X-ray light sources offer new opportunities to unravel fundamental electronic and nuclear dynamics in matter. The Chemical Dynamics program at the Ultrafast X-ray Science Laboratory is focused on the application of emerging laboratory- and accelerator-based X-ray techniques to monitor the flow of charge, mass, and energy in molecules, clusters, and interfacial systems.
A brief overview of the program will be followed by the discussion of two particular showcase examples of ongoing research: The study of photoinduced charge-transfer dynamics in dye-sensitized nanocrystals by time-resolved X-ray photoelectron spectroscopy and the investigation of quantized fluid dynamics in nano- to micron-scale superfluid helium droplets by single-shot coherent diffractive imaging. Interfacial charge transfer studies are performed at the Linac Coherent Light Source (LCLS - SLAC National Accelerator Laboratory) and the Advanced Light Source (ALS, Berkeley).
Recent LCLS results demonstrate the potential of time-resolved X-ray photoelectron spectroscopy (TRXPS) to monitor charge migration in complex interfacial systems with femtosecond time resolution, chemical sensitivity and element specificity. The visible light induced transient oxidation state of N3 dye molecules adsorbed to nanocrystalline ZnO is characterized in a concerted effort of TRXPS experiments and ab-initio calculations of the interfacial electronic structure.
The superfluid nature of helium droplets presents a rare opportunity to study the onset of macroscopic quantum phenomena in sub-micron scale systems. Pure and doped helium droplets are studied by coherent diffractive imaging (CDI) using femtosecond X-ray pulses from the LCLS. Single-shot CDI data provide the most direct access yet to droplet size- and shape-distributions as well as fundamental dynamics inside the clusters. The results will be discussed in the context of the onset of quantum vorticity in finite three-dimensional quantum systems.