2016-12-25, Rupp, Philipp, Seiffert, Lennart, Liu, Qingcao, Süßmann, Frederik, Ahn, Byungnam, Förg, Benjamin, Schäfer, Christian G., Gallei, Markus, Mondes, Valerie, Kessel, Alexander, Trushin, Sergei, Graf, Christina, Rühl, Eckart, Lee, Jinwoo, Kim, Min Su, Kim, Dong Eon, Fennel, Thomas, Kling, Matthias F., Zherebtsov, Sergey

The excitation of nanoscale near-fields with ultrashort and intense laser pulses of well-defined waveform enables strongly spatially and temporally localized electron emission, opening up the possibility for the generation of attosecond electron pulses. Here, we investigate the electron photoemission from isolated nanoparticles of different materials in few-cycle laser fields at intensities where the Coulomb field of the ionized electrons and residual ions significantly contribute to the electron acceleration process. The dependences of the electron cut-off energy on the material’s dielectric properties and electron binding energy are investigated systematically in both experiments and semi-classical simulations. We find that for sufficiently high near-field intensities the material dependence of the acceleration in the enhanced near-fields is quenched by many-particle charge-interaction.

2019, Rupp, Philipp, Burger, Christian, Kling, Nora G, Kübel, Matthias, Mitra, Sambit, Rosenberger, Philipp, Weatherby, Thomas, Saito, Nariyuki, Itatani, Jiro, Alnaser, Ali S., Raschke, Markus B., Rühl, Eckart, Schlander, Annika, Gallei, Markus, Seiffert, Lennart, Fennel, Thomas, Bergues, Boris, Kling, Matthias F.

Nanoparticles offer unique properties as photocatalysts with large surface areas. Under irradiation with light, the associated near-fields can induce, enhance, and control molecular adsorbate reactions on the nanoscale. So far, however, there is no simple method available to spatially resolve the near-field induced reaction yield on the surface of nanoparticles. Here we close this gap by introducing reaction nanoscopy based on three-dimensional momentum-resolved photoionization. The technique is demonstrated for the spatially selective proton generation in few-cycle laser-induced dissociative ionization of ethanol and water on SiO2 nanoparticles, resolving a pronounced variation across the particle surface. The results are modeled and reproduced qualitatively by electrostatic and quasi-classical mean-field Mie Monte-Carlo (M3C) calculations. Reaction nanoscopy is suited for a wide range of isolated nanosystems and can provide spatially resolved ultrafast reaction dynamics on nanoparticles, clusters, and droplets.

2019, Liu, Qingcao, Zherebtsov, Sergey, Seiffert, Lennart, Skruszewicz, Slawomir, Zietlow, Dominik, Ahn, Seongjin, Rupp, Philipp, Wnuk, Pawel, Sun, Shaohua, Kessel, Alexander, Trushin, Sergei, Schlander, Annika, Kim, Dongeon, Rühl, Eckart, Ciappina, Marcelo F., Tiggesbäumker, Josef, Gallei, Markus, Fennel, Thomas, Kling1, Matthias F.

Field localization by nanostructures illuminated with laser pulses of well-defined waveform enables spatio-temporal tailoring of the near-fields for sub-cycle control of electron dynamics at the nanoscale. Here, we apply intense linearly-polarized two-color laser pulses for all-optical control of the highest energy electron emission from SiO2 nanoparticles. For the size regime where light propagation effects become important, we demonstrate the possibility to control the preferential emission angle of a considerable fraction of the fastest electrons by varying the relative phase of the two-color field. Trajectory based semi-classical simulations show that for the investigated nanoparticle size range the directional steering can be attributed to the two-color effect on the electron trajectories, while the accompanied modification of the spatial distribution of the ionization rate on the nanoparticle surface has only a minor effect. © 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft