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Molecular-frame photoelectron angular distributions during double core-hole generation in O₂ and N₂ molecules
(2023-09-15)
Angular distributions of photoelectrons emitted upon double core-hole (DCH) generation in nitrogen and oxygen molecules are studied theoretically in the frame of a molecular reference. The respective electronic structure calculations are performed by the single center method for photoelectron kinetic energies up to 40 eV in the relaxed-core Hartree–Fock approximation. The molecular frame photoelectron angular distributions are computed for single-site and two-site DCH creation processes and further analyzed for ...
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Spatio-temporal resolution studies on a highly compact ultrafast electron diffractometer
(2015)
Time-resolved diffraction with femtosecond electron pulses has become a promising technique to directly provide insights into photo induced primary dynamics at the atomic level in molecules and solids. Ultrashort pulse duration as well as extensive spatial coherence are desired, however, space charge effects complicate the bunching of multiple electrons in a single pulse.Weexperimentally investigate the interplay between spatial and temporal aspects of resolution limits in ultrafast electron diffraction (UED) on our ...
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Coherent acoustic phonons in a coupled hexagonal boron nitride-graphite heterostructure
(2024-02-14)
Femtosecond optically excited coherent acoustic phonon modes (CAPs) are investigated in a free-standing van der Waals heterostructure composed of a 20-nm transparent hexagonal boron nitride (hBN) and a 42-nm opaque graphite layer. Employing ultrafast electron diffraction, which allows for the independent evaluation of strain dynamics in the constituent material layers, three different CAP modes are identified within the bilayer stack after the optical excitation of the graphite layer. An analytical model is used to ...
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Organic Matter Matters—The Imaginary Conductivity of Sediments Rich in Solid Organic Carbon
(2023-12-01)
Solid organic matter (OM) is a biogeochemically relevant constituent of soils and sediments. It also affects sediments' geophysical properties, but is often overlooked in hydro- and biogeophysical approaches for the characterization of the shallow subsurface. Here, we explore the potential of spectral induced polarization (SIP) to delineate OM-rich zones in the subsurface and provide insights into the mechanisms that drive OM-polarization using measurements on both field cores and artificial OM-sand mixtures. Both, ...
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Influence of Chitosan and Grape Seed Extract on Thermal and Mechanical Properties of PLA Blends
(2023-03-22)
Blends based on polylactic acid (PLA), chitosan, and grape seed extract (GE) were prepared by extrusion and injection molding. The effect of chitosan (5% and 15% on PLA basis) and natural extract (1% on PLA basis) incorporated into the PLA host matrix was explored regarding the thermal and mechanical properties. GE showed antioxidant activity, as determined by the DPPH assay method. Chitosan and GE affect the degree of crystallinity up to 30% as the polysaccharide acts as a nucleating agent, while the extract reduces ...
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Combined Funnel, Concentrator, and Particle Valve Functional Element for Magnetophoretic Bead Transport Based on Engineered Magnetic Domain Patterns
(2023-10-27)
Controlled actuation of superparamagnetic beads (SPBs) within a microfluidic environment using tailored dynamic magnetic field landscapes (MFLs) is a potent approach for the realization of point-of-care diagnostics within Lab-on-a-chip (LOC) systems. Making use of an engineered magnetic domain pattern as the MFL source, a functional LOC-element with combined magnetophoretic “funnel”, concentrator, and “valve” functions for micron-sized SPBs is presented. A parallel-stripe domain pattern design with periodically ...