Observation of laser-assisted electron scattering in superfluid helium

• Published in: Nature communications Vol. 12; no. 1; pp. 4204 - 7
• Main Authors: Treiber, Leonhard, Thaler, Bernhard, Heim, Pascal, Stadlhofer, Michael, Kanya, Reika, Kitzler-Zeiler, Markus, Koch, Markus
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.07.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/766/119/1002; 639/766/119/999; 639/766/36/1121; 639/766/36/2796; Core particles; Droplets; Elastic scattering; Electron energy; Energy transfer; Field ionization; Fluids; Free electrons; Helium; Humanities and Social Sciences; Ionization; Lasers; Liquid helium; multidisciplinary; Science; Science (multidisciplinary); Superfluidity; Vapor phases; Variable thickness
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24479-w

Laser-assisted electron scattering (LAES), a light–matter interaction process that facilitates energy transfer between strong light fields and free electrons, has so far been observed only in gas phase. Here we report on the observation of LAES at condensed phase particle densities, for which we create nano-structured systems consisting of a single atom or molecule surrounded by a superfluid He shell of variable thickness (32–340 Å). We observe that free electrons, generated by femtosecond strong-field ionization of the core particle, can gain several tens of photon energies due to multiple LAES processes within the liquid He shell. Supported by Monte Carlo 3D LAES and elastic scattering simulations, these results provide the first insight into the interplay of LAES energy gain/loss and dissipative electron movement in a liquid. Condensed-phase LAES creates new possibilities for space-time studies of solids and for real-time tracing of free electrons in liquids. Laser-assisted electron scattering (LAES) is a commonly observed strong field process in gas phase systems. Here the authors use helium droplets with core atoms and molecules to observe increased electron energy due to multiple LAES events within the droplets.