SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 83: Focus Session: Ultrafast Dynamics in Nanostructures II

O 83.1: Topical Talk

Donnerstag, 30. März 2023, 15:00–15:30, GER 38

Imaging ultrafast electron dynamics in isolated nanoparticles — •Daniela Rupp — LFKP, ETH Zurich, Switzerland

Atomic clusters and nanodroplets are used as ideal model systems over all wavelength regimes for exploring the ultrafast physical processes underlying the formation and evolution of highly excited matter. Via single-pulse single-particle coherent diffractive imaging (CDI) with the intense femtosecond pulses from short-wavelength free electron lasers (X-FELs), it became possible to study single specimen in free flight.

In CDI, the elastically scattered light forms an interference pattern that encodes the particle's structure, allowing to investigate the morphology of fragile and short-lived specimen. Also light-induced dynamics after pulsed laser excitation can be visualized by time-resolved CDI. Even changes in the electronic properties were found to be imprinted in the CDI patterns, but their time-evolution could not be investigated with typical pulse durations of 100 femtoseconds.

We recently showed that, under favorable conditions, single helium nanodroplets can be also imaged with an intense HHG source, providing much shorter pulses. In time-resolved experiments, a moderately intense near-infrared (NIR) laser pulse, too weak to ionize helium nanodroplets, dramatically changed their scattering response in the extreme ultraviolet (XUV) regime. The ability to switch the optical properties of nanoscale matter within less than a femtosecond, and observe this temporally and spatially resolved, promise to impact a broad field of science from non-linear XUV optics to ultrafast material science.