Band Configuration Research Articles

The challenge of calibrating a laser‐interferometric gravitational wave detector

AbstractIn 2015, the first direct detection of gravitational waves was reported. Data analysis indicated that the waves had originated from the violent collision of two black holes, which scattered them through space–time as Einstein predicted. That detection was made possible by many advances in measurement technology, mainly vibration isolation of the detector optics, since, at 10 Hz, the motion of the laser‐interferometric detector mirrors is at least one billion times smaller than the seismic motion of the ground. As well, it is difficult to lock the laser in the detection configuration in a large band of the spectrum; this was made possible by using many feedback and feed‐forward control loops. However, in order to meet the many demanding requirements, more than a hundred of such active systems are included in a detector to allow locked acquisition and locked stability to, eventually, reach the desired sensitivity. In this work, challenges faced to reach some of these requirements will be described and we analyze how this scenario impacts the calibration of such detectors. In order to help reduce false alarm rates and provide data for veto systems, in this work we propose a specific kind of resonant‐mass detector to operate in coincidence with laser‐interferometric ones.

Spin Crossover and Magnetic-Dielectric Bistability Induced by Hidden Pseudo-Jahn–Teller Effect

In a semi-review paper, we show that the hidden Jahn–Teller effect (JTE) and pseudo-JTE (PJTE) in molecular systems and solids, under certain conditions lead to the formation of two coexisting stable space configurations with different magnetic and dielectric properties, switchable by external perturbations. One of the stable configurations has a high space symmetry and a non-zero or higher spin (HS) (non-zero magnetic moment), the other being distorted, but with zero or lower spin (LS). The number of systems with hidden JTE or PJTE is innumerable; we demonstrate this on the (no exhaustible, too) group of systems with half-filed closed-shell degenerate electronic (orbital or band) configurations e2 and t3. The spin-crossover-change from the high symmetry HS arrangement to the low-symmetry LS geometry is accompanied by (driven by the PJTE) orbital disproportionation, in which the system prefers spins-paired states with two electrons on the same orbital (and lower symmetry charge distribution) over the Hund’s spin-parallel arrangement involving several orbitals. Ab initio calculations previously carried out on a series of molecular systems and clusters in crystals, including CuF3, Si3, Si4, Ge4, C4H4, Na4−, C603−, CuO6 (in two crystal environments, LiCuO2 and NaCuO2), etc., confirmed the general theory and allowed for estimates of the parameter values including relaxation times. The hidden JTE and PJTE are thus general tools for search and studies of polyatomic systems with bistabilities.

Investigation on the mechanically-induced nanocrystallization in metallic glasses

Shear-induced nanocrystallization in bent ribbons of Pd40Cu30Ni10P20 metallic glass has been quantitatively investigated via synchrotron radiation. The formed nanocrystals volume fraction during deformation has been directly estimated from X-ray diffraction spectra using peaks area integration. The nanocrystallization process during deformation was found to be strongly linked with the microstructure configuration of shear bands in amorphous alloys. A constitutive model based on free volume approach has been introduced to describe the kinetic of mechanically induced nanocrystallization. The solution of the coupled constitutive equations of the model, fitted to experimental data, permits to determine the physical and mechanical parameters governing the phenomena of shear-induced crystallization in metallic glasses.

Insitu growth of BiVO4/HoVO4 heterojunction with O[sbnd]O bond connection for enhanced photodegradation activity

Heterojunction composite plays an important role in enhancing photocatalysis activity through inhibit electron-hole recombination. In this paper, biphasic heterojunction BiVO4 and HoVO4 is insitu-grown and characterized through XRD, TEM, Raman, SEM, EDS, and XPS. These two structures form n type staggered band configuration using Mott-Schottky and DRS. Rhodamine B (RhB) photodegradation efficiency of the optimal sample is 90.7% after 90 min, higher than single BiVO4 54% and HoVO4 34.5%. The main reason is ascribed to fast photogenerated charge separation via OO bond connection according to photoluminescence, photocurrent response, and theory calculation. The RhB degradation path is revealed from intermediate products identification. Therefore this study unveils photodegradation dyes application of BiVO4/HoVO4 samples.

Novel Z-Scheme/Type-II CdS@ZnO/g-C3N4 ternary nanocomposites for the durable photodegradation of organics: Kinetic and mechanistic insights

Visible-light-driven photocatalysis is a green and efficient strategy for wastewater treatment, where graphitic carbon nitride-based semiconductors showed excellent performance in this regard. Consequently, we report on the development of a green and facile one-pot room-temperature ultrasonic route for the preparation of novel ternary nanocomposite of cadmium sulfide quantum dots (CdS QDs), zinc oxide nanoparticles (ZnO NPs), and graphitic carbon nitride nanosheets (g-C3N4 NSs). The proposed materials had been characterized by several physicochemical techniques such as PXRD, XPS, FE-SEM, HR-TEM, PL, and DRS. The photocatalytic efficiency of the proposed photocatalysts was assessed towards the photodegradation of Rhodamine B dye as a water pollutant model using spectrophotometric measurements. The as-synthesized novel ternary nanocomposite (CdS@ZnO/g-C3N4) exhibited perfect photocatalytic activity, where almost complete degradation was achieved in only 2 h under UV-irradiation or 3 h under visible-irradiation. Various methods were used to elucidate the kinetics of the photocatalytic process. Moreover, CdS@ZnO/g-C3N4 exhibited a unique synergetic performance when compared to the corresponding binary composites or the individual components. This synergetic performance could be ascribed to the perfect electronic band configuration of the three components, leading to the establishment of several combined synergetic Z-Scheme/Type-II photocatalytic heterojunctions, which is the proposed mechanism for the observed synergetic photocatalytic reactivity of the as-synthesized CdS@ZnO/g-C3N4 nanocomposite when compared to the single and binary nanocomposite counterparts. Furthermore, the effects of both the type and concentration of various scavengers on the photocatalytic activity were assessed to investigate the most reactive species, where the reductive degradation pathway was found to be the predominant route. Finally, the photocatalytic efficiency of the as-synthesized CdS@ZnO/g-C3N4 composite showed promising and competing results when compared to other photocatalysts reported in the literature.

Size Effect in Plastic Deformation and Failure of Metallic Glasses

Depending on the composition and structure of metallic glasses cells with the dimensions in the range from tenths nanometers to tenths micrometers were observed on the ductile fracture surface. The variation in dimple size was compared with the serrations presented on the loading curve at the nanoindentation of the metallic glasses with different compositions. Higher instantaneous deformation can be connected with simultaneous shearing at more suitable shear band configurations. The cell morphology with the various cell sizes is observed at the failure of the metallic glasses. At the failure of high strength metallic glasses, the cells are formed in short time due to the release of high amount of stored elastic energy. In this case the uniform cell morphology with the cell size of about 20 nm is observed.

Electrical Properties of Al2O3/ZnO Metal–Insulator–Semiconductor Capacitors

An Al2O3 thin film is assembled on an unin- tentionally doped ZnO for metal–insulator–semiconductor (MIS) capacitors. Leakage current density ( ${J}$ ), capacitance–voltage ( ${C} - {V}$ ) properties, and their thermal stabilities are investigated. The ${J}$ -values for the MIS capacitors before and after annealing at 300 °C are lower than $2.0 \times 10^{-7}$ A/cm2 at a gate voltage of −10.0~10.0V. Frequency-dependent ${C}-{V}$ characteristic shows a stable maximum capacitance for the MIS capacitor before annealing. However, it decreases dramatically at 1 MHz for that after annealing at 300 C, which is attributed to the change of ZnO channel resistance. Flat band voltage shifts in the–curves after annealing at 300 C are one order lower than those before annealing, indicating the decrease of positive fixed charge density in the Al2O3 film. There are ledge phenomena for hysteresis characteristics in the curves, which result possibly from the delayed evacuation of minority carriers in deep depletion region. By considering the Fowler–Nordheim tunneling model, band configurations of the Al2O3/ZnO heterojunctions are clarified to be straddling gap structures with conduction band offsets larger than 1.3 eV.

Lignin‐Incorporated Supramolecular Copolymerization Yielding g‐C3N4 Nanoarchitectures for Efficient Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g‐C3N4)‐based nanostructures are a fast‐growing family of metal‐free semiconductors that have attracted much attention as hydrogen‐evolving photocatalysts. Previous research mostly uses small organic molecules to modify g‐C3N4 for improved solar‐to‐fuel conversion efficiency; however, there are scarce reports on high‐efficiency g‐C3N4 photocatalysts modified with natural macromolecules. Herein, lignin‐modified g‐C3N4 nanoarchitectures with an ultrathin layered topography are successfully synthesized. The biomass‐modified g‐C3N4 photocatalyst obtained through this method delivers a hydrogen‐evolving rate of 2235 μmol g−1 h−1, which is 3.5 times higher than that of g‐C3N4 calcined from the preorganized cyanuric acid–melamine supramolecular assemblies. On the basis of experimental evidences, the improved hydrogen evolution reaction (HER) performance is attributed to synergistic effects between the ultrathin few‐layer 2D nanostructure, extended visible light absorption, and ideal energy band configuration. The biomass‐activated g‐C3N4 nanostructures prepared via this synthesis route prove suitable for use as cost‐effective and efficient photocatalysts for scalable solar hydrogen production.

Band structures, lifetimes, and shape coexistence in La130

The level structure of $^{130}\mathrm{La}$ has been investigated using the $^{121}\mathrm{Sb}(^{12}\mathrm{C}$, 3n) reaction with the ROSPHERE array at IFIN-HH, Bucharest. The level scheme was significantly extended with the observation of 45 new states and 100 new transitions. Several band structures have been identified and a clear connection with the lower-lying states has been established. A lifetime of $\ensuremath{\tau}=3.6(2)$ ns has been measured for the 346-keV ${6}^{\ensuremath{-}}$ state by the in-beam fast timing technique. The lifetimes of 18 high-spin states have been determined by applying the Doppler-shift attenuation method. The deformations derived from the experimental $B(E2)$ transition strengths indicate distinct coexisting shapes at high spins in $^{130}\mathrm{La}$. The experimental properties of both low- and high-spin states were compared with theoretical calculations performed in the frame of the two-quasiparticles-plus-rotor model. Two new negative-parity decoupled bands, with a deduced quadrupole deformation ${\ensuremath{\beta}}_{2}=0.150(15)$, were interpreted by coupling the proton in the 1/2[550] and 3/2[541] orbitals with the odd neutron occupying mainly the low-$\mathrm{\ensuremath{\Omega}}$ orbitals from the ${d}_{3/2}$ and ${s}_{1/2}$ states. A quadrupole deformation ${\ensuremath{\beta}}_{2}=0.220(17)$ was derived for a newly identified positive-parity decoupled band. This enhanced deformation was attributed to the involvement in the band configuration of the $\mathrm{\ensuremath{\Omega}}=1/2$ $({f}_{7/2},{h}_{9/2})$ intruder neutron orbital. The multiparticle configuration $\ensuremath{\pi}{g}_{7/2}{({h}_{11/2})}^{2}\ensuremath{\bigotimes}\ensuremath{\nu}({h}_{11/2})$ was assigned to a high-spin negative-parity dipole band, based on the comparison of the experimental $B(M1)$ transition strengths with values calculated by applying the geometrical model of D\onau and Frauendorf.

Design and Fabrication of a Holographic Radial Polarization Converter

Radial polarization converters can convert an incident light into a radially polarized light, which is beneficial in a variety of applications. In this paper, a new design of holographic radial polarization converter is proposed which consists of eight space-variant polarization-selective volume hologram gratings. According to the coupled wave theory, a feasible design of the polarization-selective volume hologram gratings was described. The prism-hologram-prism sandwiched recording method was adopted for the recording. The s- and p-polarization diffraction efficiencies of the fabricated polarization-selective volume hologram gratings at 443.29 nm are 90.83% and 22.09%, respectively. The operation bandwidth is about 4.42 nm. A prototype of holographic radial polarization converter was successfully assembled and tested. Due to the introduction of volume hologram gratings, this design should have the advantages of high diffraction efficiency, narrow band, compactness, and planar configuration, meaning it is especially suitable for low-cost mass production and has high application potential in related fields.

<p><strong><em>Ctenophora sinensis</em>: a new diatom species (Bacillariophyta) from China with comments on its structure, nomenclature and relationships</strong></p>

Lake Qinghai is an ancient brackish water lake in the Qinghai province of China. A number of endemic diatom species have already been discovered and described from the lake. This study describes another new endemic diatom species: Ctenophora sinensis sp. nov. Ctenophora sinensis has the following features: (1) frustule and valve are lanceolate; (2) the central area is slightly buttressed internally; (3) its areolae have both outside sieve-like closing plates and inside hymenate occlusions; (4) an apical hyaline field exists near each rimoportula; (5) a pseudoseptum is always presents at each pole; and (6) the cingulum has a 4:2 configuration of girdle bands in normal vegetative cells. Some remarks are provided on the nomenclature of Ctenophora and a few comments on the relationships of the genus.

Novel Cu2ZnSnS4/Pt/g-C3N4 heterojunction photocatalyst with straddling band configuration for enhanced solar to fuel conversion

In the context of efficient conversion of CO2 to high-value carbonaceous fuels, the development of photocatalysts for CO2 reduction having high solar-to-fuel energy efficiency with exceptional selectivity and long-term stability is the prime requisite of current research. Herein, we reported a novel straddling band configuration based Cu2ZnSnS4/Pt-integrated g-C3N4 heterojunction photocatalyst for CO2 reduction to carbonaceous fuels. The heterojunction photocatalyst exhibited an enhanced CO2 reduction with an average CO/CH4 yield rates of 17.351/7.961 μmolg−1 h−1, which is ∼3.31 and ∼5.56 folds higher than pristine g-C3N4. The comprehensive analysis of heterojunction photocatalyst exhibited synergetic effects owing to higher surface area, efficient photon harvesting due to CZTS and multiple charge-transfer pathways together with Z-scheme charge transfer. Moreover, the localized surface-plasmon-resonance (LSPR) and electron sink function of Pt led to an efficient interfacial charge carrier separation, surface site activation for CO2 reduction and in the consequence of that enhanced the photocatalytic performance.

Coverage Layer Phase Composition-Dependent Photoactivity of One-Dimensional TiO2-Bi2O3 Composites.

TiO2–Bi2O3 composite rods were synthesized by combining hydrothermal growth of rutile TiO2 rod templates and sputtering deposition of Bi2O3 thin films. The TiO2–Bi2O3 composite rods with β-Bi2O3 phase and α/β-Bi2O3 dual-phase decoration layers were designed, respectively, via in situ radio-frequency magnetron sputtering growth and post-annealing procedures in ambient air. The crystal structure, surface morphology, and photo-absorption performances of the pristine TiO2 rods decorated with various Bi2O3 phases were investigated. The crystal structure analysis reveals that the crystalline TiO2–Bi2O3 rods contained β-Bi2O3 and α/β-Bi2O3 crystallites were separately formed on the TiO2 rod templates with different synthesis approaches. The morphology analysis demonstrates that the β-Bi2O3 coverage layer on the crystalline rutile TiO2 rods showed flat layer morphology; however, the surface morphology of the α/β-Bi2O3 dual-phase coverage layer on the TiO2 rods exhibited a sheet-like feature. The results of photocatalytic decomposition towards methyl orange dyes show that the substantially improved photoactivity of the rutile TiO2 rods was achieved by decorating a thin sheet-like α/β-Bi2O3 coverage layer. The effectively photoinduced charge separation efficiency in the stepped energy band configuration in the composite rods made from the TiO2 and α/β-Bi2O3 explained their markedly improved photoactivity. The TiO2-α/β-Bi2O3 composite rods are promising for use as photocatalysts and photoelectrodes.

The Retrieval of Total Precipitable Water over Global Land Based on FY-3D/MWRI Data

Total precipitable water (TPW) is an important key factor in the global water cycle and climate change. The knowledge of TPW characteristics at spatial and temporal scales could help us to better understand our changing environment. Currently, many algorithms are available to retrieve TPW from optical and microwave sensors. There are still no available TPW data over land from FY-3D MWRI, which was launched by China in 2017. However, the TPW product over land is a key element for the retrieval of many ecological environment parameters. In this paper, an improved algorithm was developed to retrieve TPW over land from the brightness temperature of FY-3D MWRI. The major improvement is that surface emissivity, which is a key parameter in the retrieval of TPW in all-weather conditions, was developed and based on an improved algorithm according to the characteristics of FY-3D MWRI. The improvement includes two aspects, one is selection of appropriate ancillary data in estimating surface emissivity parameter Δε18.7/Δε23.8 in clear sky conditions, and the other is an improvement of the Δε18.7/Δε23.8 estimation function in cloudy conditions according to the band configuration of FY-3D MWRI. Finally, TPW retrieved was validated using TPW observation from the SuomiNet GPS and global distributed Radiosonde Observations (RAOB) networks. According to the validation, TPW retrieved using observations from FY-3D MWRI and ancillary data from Aqua MODIS had the best quality. The root mean square error (RMSE) and correlation coefficient between the retrieved TPW and observed TPW from RAOB were 5.47 and 0.94 mm, respectively.

Multiscale structure and band configuration tuning to achieve high thermoelectric properties in n-type PbS bulks

PbS shares several similar features with PbTe and PbSe, and it is much more earth-abundant and inexpensive, which is characteristic of promising Te/Se-free thermoelectric materials for intermediate temperature power generation. However, its thermal conductivity is much higher than those of PbTe and PbSe, which bring a big challenge for obtaining high-performance PbS. In this study, we rationally integrate multiscale structure involving point defects, nanoprecipitates, grain boundaries and dislocations in PbS by doping for decreasing lattice thermal conductivity and simultaneously tuning energy band configuration. Density functional theory (DFT) calculations demonstrate that the ClS–SbPb defects with the lowest formation energy create an obvious shallow donor band and push upward-moving Fermi level, in good agreement with high electrical transport properties. Remarkably, PbS-0.067%PbCl2-1.5%Sb sample presents outstanding ZT of ~1.0 at 823 K and averaged ZT of ~0.62 at 423–823 K due to a low lattice thermal conductivity and a high power factor.

Type-II heterojunction constructed by Ag2S-coupled ZnO microspheres with visible light-responsive antibacterial activity

ZnO nanorods-assembled microspheres were photosensitized with a layer of low bandgap Ag2S nanoparticles on the branched nanorods to get a type-II core/shell heterojunction (ZnO@Ag2S). The heterojunction with unique band configuration exhibited better visible light-responsive antibacterial activity than pure ZnO, which is attributed to the inhibition of photocarrier recombination and efficient charge separation and transfer. Scavenger test confirmed that the photoinactivation of bacteria was directed by the combined assistance of O2− radicals and photogenerated holes. The growth of Gram-negative bacteria was more effectively restrained by ZnO@Ag2S than that of Gram-positive bacteria and fungi because of structural difference of cell walls.

Two-dimensional hole gas formed at diamond surface by Al2O3/diamond interface engineering

Understanding and rationally controlling the interfacial electronic states of the Al2O3/diamond (Al2O3(001)/C(001)) appears to be crucial in the next generation oxide-semiconductor devices on the basis of diamond. In this work, the density functional theory computations are used to systematically elucidate the effects of the different terminated planar of Al2O3 and diamond on the electronic properties of the Al2O3/diamond interfaces. Results show that a two-dimensional hole gas can be created at the Al2O3(001)/C(001) heterointerface. In particular, for the most stable CAl interface under Al-rich condition, a strong p-type doping with obvious localization characteristics from charge transfer is achieved, which reveals a 2DHG generated at the CAl interface. Bader analysis reveals that the 0.047 e/unit-cell are transferred from the side of diamond into the side of Al2O3. In addition, the band alignments of Al2O3(001)/C(001) hetero–interface show a type-II staggered band configuration, and a VBO of 3.5 eV is independent of strain for the most stable CAl interface. The observation of the 2DHG at the CAl interface and the positive valence band offset will provide a practical guidance for further investigation for future diamond-based power devices.

Search for the high-spin members of the α:2n:α band in Be10

Method: Measuring excitation functions for $^{6}$He+$\alpha$ scattering, populating states in the excitation energy range from 4.5 MeV to 8 MeV in $^{10}$Be using a $^6$He rare-isotope beam and a thick helium gas target. Results: No new excited states in $^{10}$Be have been observed. Stringent limitation on the possible degree of $\alpha$-clustering of the hypothetical yrast 6$^+$ state has been obtained. Conclusions: The high-spin members of the $\alpha$:2n:$\alpha$ molecular-like rotational band configuration, that is considered to have a 0$^+$ bandhead at 6.18 MeV, either do not exist or have small overlap with the $^{6}$He(g.s.)+$\alpha$ channel.

Wideband UHF Antenna for Partial Discharge Detection

This paper presents a ultra-high frequency (UHF) antenna for partial discharge (PD) detection and the antenna sensor can be used near a conducting ground wire. The proposed UHF antenna has advantages of easy setup and higher-frequency detection over the high-frequency current transformer (HFCT) sensor. First, a variety of loop-shaped antennas are designed to compare each near field coupling capability. Then, a new UHF antenna is designed based on the loop-shaped antenna, which has the best near field coupling capability. Finally, the proposed UHF antenna is fabricated and measured. It provides a wide impedance bandwidth of 760 MHz (740–1500 MHz). Its simple setup configuration and wide bandwidth frequency response in the UHF band can provide a more efficient means for PD detection.

Ionization of adenine in the presence of Na+ in the gas phase and water

In this work, the photoelectron spectrum of adenine (AD) interacting with one and two bare and microhydrated Na+ (AD-Na+, Na+-AD-Na+, AD-[Na(H2O)n]+ and [Na(H2O)n]+-AD-[Na(H2O)n]+) have been calculated in two environments including the gas phase and water, separately. The symmetry adapted/cluster configuration interaction (SAC-CI) methodology was employed to calculate the first to fifth ionization energies (IEs) of AD. The photoelectron spectra of AD-Na+ structures showed a shift to higher binding energy, depending on the interaction site of Na+, compared to the spectrum of bare AD in gas phase while a slight shift to lower binding energy was observed for the spectrum of the most stable structure of AD-Na+ in water compared to bare AD in the same condition. In the presence of second Na+, the gas phase photoelectron spectrum of Na+-AD-Na+ shifted to higher binding energy compared to the spectrum of AD-Na+. This energy shift was nearly independent of the interaction site of second Na+ and decreased, considerably in the water environment. The microhydration of Na+ in the AD-Na+ and Na+-AD-Na+ structures in the gas phase, shifted their photoelectron spectra to lower binding energies compared to the spectra of corresponding unhydrated structures depending on the number of water molecules. A similar trend was also observed in water. The hydration of Na+ could decrease the ionization energy of AD-Na+ and Na+-AD-Na+ structures in water even lower than the ionization energies of bare AD in the same conditions. The main electronic configurations of the ionization bands of each structure were determined and their changing with the Na+ interaction site, number of Na+ and hydration of Na+ were explained. The kind and contribution of Lewis orbitals in the canonical molecular orbitals participating in ionization were determined for each structure.