5 research outputs found
Phase-locking of time-delayed attosecond XUV pulse pairs
We present a setup for the generation of phase-locked attosecond extreme ultraviolet (XUV) pulse pairs. The attosecond pulse pairs are generated by high harmonic generation (HHG) driven by two phase-locked near-infrared (NIR) pulses that are produced using an actively stabilized Mach-Zehnder interferometer compatible with near-single cycle pulses. The attosecond XUV pulses can be delayed over a range of 400 fs with a sub-10-as delay jitter. We validate the precision and the accuracy of the setup by XUV optical interferometry and by retrieving the energies of Rydberg states of helium in an XUV pump–NIR probe photoelectron spectroscopy experiment
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Field-Induced Tunneling Ionization and Terahertz-Driven Electron Dynamics in Liquid Water
Liquid water at ambient temperature displays ultrafast molecular motions and concomitant fluctuations of very strong electric fields originating from the dipolar H2O molecules. We show that such random intermolecular fields induce the tunnel ionization of water molecules, which becomes irreversible if an external terahertz (THz) pulse imposes an additional directed electric field on the liquid. Time-resolved nonlinear THz spectroscopy maps charge separation, transport, and localization of the released electrons on a few-picosecond time scale. The highly polarizable localized electrons modify the THz absorption spectrum and refractive index of water, a manifestation of a highly nonlinear response. Our results demonstrate how the interplay of local electric field fluctuations and external electric fields allows for steering charge dynamics and dielectric properties in aqueous systems. Copyright © 2020 American Chemical Society
Field-Induced Tunneling Ionization and Terahertz-Driven Electron Dynamics in Liquid Water
Liquid water at ambient temperature displays ultrafast molecular motions and
concomitant fluctuations of very strong electric fields originating from the
dipolar H2O molecules. We show that such random intermolecular fields induce
tunnel ionization of water molecules, which becomes irreversible if an external
terahertz (THz) pulse imposes an additional directed electric field on the
liquid. Time-resolved nonlinear THz spectroscopy maps charge separation,
transport and localization of the released electrons on a few-picosecond time
scale. The highly polarizable localized electrons modify the THz absorption
spectrum and refractive index of water, a manifestation of a highly nonlinear
response. Our results demonstrate how the interplay of local electric field
fluctuations and external electric fields allows for steering charge dynamics
and dielectric properties in aqueous systems
Field-Induced Tunneling Ionization and Terahertz-Driven Electron Dynamics in Liquid Water
Nanocomposites of Highly Monodisperse Encapsulated Superparamagnetic Iron Oxide Nanocrystals Homogeneously Dispersed in a Poly(ethylene Oxide) Melt
Nanocomposite materials based on highly stable encapsulated superparamagnetic iron oxide nanocrystals (SPIONs) were synthesized and characterized by scattering methods and transmission electron microscopy (TEM). The combination of advanced synthesis and encapsulation techniques using different diblock copolymers and the thiol–ene click reaction for cross-linking the polymeric shell results in uniform hybrid SPIONs homogeneously dispersed in a poly(ethylene oxide) matrix. Small-angle X-ray scattering and TEM investigations demonstrate the presence of mostly single particles and a negligible amount of dyads. Consequently, an efficient control over the encapsulation and synthetic conditions is of paramount importance to minimize the fraction of agglomerates and to obtain uniform hybrid nanomaterials