A calculation of the second-order (rescattering) term in the S-matrix expansion of above-threshold ionization is presented for the case when the binding potential is the unscreened Coulomb potential. Technical problems related to the divergence of the Coulomb scattering amplitude are avoided in the theory by considering the depletion of the atomic ground state due to the applied laser field, which is well defined and does not require the introduction of a screening constant. We focus on the low-energy structure, which was observed in recent experiments with a midinfrared wavelength laser field. Both the spectra and, in particular, the observed scaling versus the Keldysh parameter and the ponderomotive energy are reproduced. The theory provides evidence that the origin of the structure lies in the long-range Coulomb interaction.
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http://dx.doi.org/10.1103/PhysRevLett.110.013001 | DOI Listing |
Nanomaterials (Basel)
January 2025
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.
We used density functional theory with a hybrid functional to investigate the structure and properties of [4H] (hydrogarnet) defects in -quartz as well as the reactions of these defects with electron holes and extra hydrogen atoms and ions. The results demonstrate the depassivation mechanisms of hydrogen-passivated silicon vacancies in -quartz, providing a detailed understanding of their stability, electronic properties, and behaviour in different charge states. While fully hydrogen passivated silicon vacancies are electrically inert, the partial removal of hydrogen atoms activates these defects as hole traps, altering the defect states and influencing the electronic properties of the material.
View Article and Find Full Text PDFGels
January 2025
Department of Materials, "Vinča" Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia.
The formation of an aluminosilicate gel structure made of alkali-activated materials (AAMs) was conducted through an alkali-activation reaction of the solid precursors (fly ash, metakaolin, and wood ash). Fly and wood ash are by-products of the burning process of coal and wood, respectively. Alkali-activated materials of aluminosilicate origin, made from the different ashes, fly and wood, are very attractive research targets and can be applied in various technological fields due to their thermal stability, resistance to thermal shock, high porosity, high sustainability, and finally, low energy loss during production.
View Article and Find Full Text PDFiScience
January 2025
School of Mechanical Engineering, Tongji University, Shanghai 201804, China.
Thermo-responsive polymer is becoming a potential water purification and water harvesting material. To clarify the water diffusion characteristics, the desorption ratio of liquid water and water vapor for a poly (N-isopropylacrylamide) was researched by the multi-scale method. Firstly, macro and micro structures for the hydrogel with different water content were characterized.
View Article and Find Full Text PDFNature
January 2025
Department of Physics, Columbia University, New York, NY, USA.
The discovery of superconductivity in twisted bilayer and trilayer graphene has generated tremendous interest. The key feature of these systems is an interplay between interlayer coupling and a moiré superlattice that gives rise to low-energy flat bands with strong correlations. Flat bands can also be induced by moiré patterns in lattice-mismatched and/or twisted heterostructures of other two-dimensional materials, such as transition metal dichalcogenides (TMDs).
View Article and Find Full Text PDFACS Nano
January 2025
Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic.
Blue phosphorene, a two-dimensional, hexagonal-structured, semiconducting phosphorus, has gained attention as it is considered easier to synthesize on metal surfaces than its allotrope, black phosphorene. Recent studies report different structures of phosphorene, for example, on Cu(111), but the underlying mechanisms of their formation are not known. Here, using a combination of in situ ultrahigh vacuum low-energy electron microscopy and in vacuo scanning tunneling microscopy, we determine the time evolution of the surface structure and morphology during the deposition of phosphorus on single-crystalline Cu(111).
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