Seminar: Markus Koch
We invite you to a seminar by Associate Professor Markus Koch from Institute of Experimental Physics, Graz University of Technology, Austria, January 3 at 10:00 in C413 at HCØ. The seminar is titled "Ultrafast Photoexcitation Dynamics of Atoms and Molecules in a Quantum Solvent."
Superfluid helium nanodroplets (HeN), which have been routinely used for decades to syn-thesize weakly bound molecules, represent a novel sample preparation technique to study ultrafast dynamics in previously inaccessible systems. Here I present first time-resolved in-vestigations of single indium (In) atoms and In2 molecules located inside HeN, obtained with a combination of time-resolved photoelectron spectroscopy and time-dependent density func-tional theory modelling. For In atoms we find that photoexcitation leads to expansion of the solvation shell (He bubble) within ~600 fs (Fig. 1a), accompanied by conversion of In excited-state electronic energy into He pressure waves . This process triggers a collective oscilla-tion of the He bubble with a period of (28±1) ps, and ultimately leads to ejection of the dopant from the droplet after ~60 ps. In2 (Fig. 1b) show additionally pronounced wave packet dy-namics with the appearance of revivals after ejection from the droplet, providing insight into the quantum solvent-induced decoherence of nuclear motion. Both results demonstrate the feasibility of femtochemistry experiments inside HeN.
 B. Thaler, S. Ranftl, P. Heim, S. Cesnik, L. Treiber, R. Meyer, A. W. Hauser, W. E. Ernst, M. Koch, Nature Communications 9, 4006 (2018)