Garchinger Maier-Leibnitz-Kolloquium: Real-time optical-streak of laser-accelerated ion induced electron solvation in liquid water

by Alexander Praßelsperger (LMU Munich)

Lecture Hall, ground floor (west) (LMU building, Am Coulombwall 1, Campus Garching)

Lecture Hall, ground floor (west)

LMU building, Am Coulombwall 1, Campus Garching


Since the 2000s ion-acceleration by high-power laser systems has boosted a global interest in the physics of this compact source of energetic particles with exceptional properties. The bunches inherently contain large numbers of particles bunched in durations of only a few picoseconds when applied in immediate distance to the source. Moreover, the possibility to pick a probe pulse from the acceleration-driving-laser predestines to study fundamental ion-matter-interactions with temporal resolution that has so far, for protons and ions, not been accessible. As proposed by Gauduel et al. [1] the energy dissipation time within ion tracks can be expected to be higher compared to electron and EM-radiation tracks due to the very high energy deposition in small localised volumes, especially in the Bragg-peak. With an optical streaking setup we were able to confirm this delayed thermalisation experimentally for the first time by imprinting the temporal evolution of the ion-matter-interaction into the spectrum of a chirped probe pulse via solvated electron absorption [2]. Solvation here describes a localised state where a previously ionised electron binds to broken hydrogen-bonds which is absorbing exactly in the wavelength region of our lasers around 800 nm. Our measurements revealed a >20 ps delay in electron solvation when compared to common models assuming a lower local energy density. This indicates that so far neglected forces might affect electron dynamics. Investigating this currently unexplored parameter range, with high peak current ion bunches in sub-nanosecond durations, represents a great opportunity for improving our understanding of the thermalisation process within ion tracks on ultra-short timescales, with potential implications, e.g., for ionoacoustics, determination of the ions' radiobiological effectiveness (RBE) or the flash-effect in radiobiology, to name just a few applications [3].

[1] Y. A. Gauduel et al. Eur. Phys. J. D 60 (2010) 121
[2] A. Prasselsperger et al. Phys. Rev. Lett. 127 (2021) 186001
[3] P. R. Bolton et al. CRC Press, Taylor & Francis Group ed1 (2018) ISBN 14987\66412

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Organized by

Peter Thirolf (LMU) / Norbert Kaiser (TUM)