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 [1]. 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.

[1] 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)