Mechanisms of 1s Double-Core-Hole Excitation and Decay in Neon

The formation and decay of double-core-hole (DCH) states of the neon ion irradiated by an intense electromagnetic x-ray field are studied theoretically. In the present research DCH formation is the result of sequential absorption of two photons with the creation of an intermediate ion. Detailed calculations of the partial decays and probabilities of shake-ups at the atomic and ionic ionization stages are presented. The angular distribution of photoelectrons corresponding to various residual ionic states are calculated. Specifically, we predict the lack of any photoelectrons corresponding to the residual ionic state 1s12s22pnmpn′2Sf+1D in the direction of the electric field polarization. Dynamical competition between single-core-hole state decay and excitation is analyzed and pulse parameters corresponding to various dynamical regimes are found.

Polyvinylidene Fluoride-Based Metasurface for High-Quality Active Switching and Spectrum Shaping in the Terahertz G-Band

We report theoretical investigations performed in the terahertz G-band, in the 228–232 GHz spectral window for a piezoelectrically-responsive ring-cone element metasurface composed of polyvinylidene fluoride (PVDF)/Silicon and PVDF/Silica glass. The choosing of this spectral window is motivated by a multitude of applications in terahertz detection and terahertz imaging, that commonly make use of this band. The uniqueness of the envisioned architecture resides in the combination between the readily-available polyvinylidene fluoride polymer and silicon/silica glass substrates, together with the introduction of an extra degree of freedom, in the form of a ring-cone architecture , and the active control of the geometric sizes through the longitudinal piezoelectric effect exhibited by the polymer. The spectral response of the metasurface is dependent on the combination between the polymer elements and the substrate, and ranges from near-zero absorption switching to a resonant behavior and significant absorption. The interaction between the electromagnetic field and the polymer-based metasurface also modifies the phase of the reflected and transmitted waves over a full 2π range, permitting complete control of the electric field polarization. Moreover, we take advantage of the longitudinal piezoelectric effect of PVDF and analyze the spectrum shaping capability of the polymer-based metasurface. Our analysis highlights the capability of the proposed architecture to achieve complete electric field polarization control, near-zero optical switching and resonant behavior, depending on the geometries and sizes of the architecture elements resulting from construction considerations and from the externally applied voltages through the piezoelectric effect.

Heteroatom coordination induces electric field polarization of single Pt sites to promote hydrogen evolution activity

Herein, we reported a kind of single Pt sites (Pt-SA) stabilized on an MXene support (Pt-SA/MXene) via the formation of Pt-O and Pt-Ti bonds to effectively catalyze the hydrogen evolution...

Transport ratios of the kinetic Alfvén mode in space plasmas

<p>Electric field properties of the kinetic Alfvén mode are analytically studied by constructing the dielectric tensor of the plasma using the linear Vlasov theory and reducing (and identifying) the tensor elements into that of the fluid picture such as the polarization drift, the Hall current, and the diamagnetic current. Off-diagonal dielectric responses do not primarly contribute to the dispersion relation of the kinetic Alfvén mode, but play an important role in the electric field polarization (field rotation sense around the mean magnetic field) and parallel component of the field. The polarization becomes more circular and the parallel component enhances at larger perpendicular wavenumbers. Analytic expression of fluctuation sense serves as a tool to identify the kinetic Alfvén mode in space plasma observations.</p>

Photocatalytic water splitting by N-TiO2 on MgO (111) with exceptional quantum efficiencies at elevated temperatures

Photocatalytic water splitting is attracting enormous interest for the storage of solar energy but no practical method has yet been identified. In the past decades, various systems have been developed but most of them suffer from low activities, a narrow range of absorption and poor quantum efficiencies (Q.E.) due to fast recombination of charge carriers. Here we report a dramatic suppression of electron-hole pair recombination on the surface of N-doped TiO2 based nanocatalysts under enhanced concentrations of H+ and OH−, and local electric field polarization of a MgO (111) support during photolysis of water at elevated temperatures. Thus, a broad optical absorption is seen, producing O2 and H2 in a 1:2 molar ratio with a H2 evolution rate of over 11,000 μmol g−1 h−1 without any sacrificial reagents at 270 °C. An exceptional range of Q.E. from 81.8% at 437 nm to 3.2% at 1000 nm is also reported.

Wettability control of conjugated polymer films by electric-field polarization technique

The wettability of conjugated polymer poly(3-hexylthiophene) (P3HT) films was accurately controlled by an electric field polarization technique, and transition of the films from being hydrophobic to hydrophilic was successfully achieved.