Steering the energy sharing of electrons in nonsequential double ionization with orthogonally polarized two-color field

Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)laser field is theoretically studied.And the dynamics in two typical collision pathways,recollision-impact-ionization(RII)and recollisionexcitation with subsequent ionization(RESI),is systematically explored.Our results reveal that the V-shaped structure in the correlated momentum distribution is mainly caused by the RII mechanism when the relative amplitude of the OTC laser field is zero,and the first ionized electrons will quickly skim through the nucleus and share few energy with the second electron.As the relative amplitude increases,the V-shaped structure gradually disappears and electrons are concentrated on the diagonal in the electron correlation spectrum,indicating that the energy sharing after electrons collision is symmetric for OTC laser fields with large relative amplitudes.Our studies show that changing the relative amplitude of the OTC laser field can efficiently control the electron–electron collisions and energy exchange efficiency in the NSDI process.

Mott Gap Filling by Doping Electrons through Depositing One Sub-Monolayer Thin Film of Rb on Ca_(2)CuO_(2)Cl_(2)

Understanding the doping evolution from a Mott insulator to a superconductor probably holds the key to resolve the mystery of unconventional superconductivity in copper oxides. To elucidate the evolution of the electronic state starting from the Mott insulator, we dose the surface of the parent phase Ca_(2)CuO_(2)Cl_(2) by depositing Rb atoms, which are supposed to donate electrons to the CuO_(2) planes underneath. We successfully achieved the Rb sub-monolayer thin films in forming the square lattice. The scanning tunneling microscopy or spectroscopy measurements on the surface show that the Fermi energy is pinned within the Mott gap but close to the edge of the charge transfer band. In addition, an in-gap state appears at the bottom of the upper Hubbard band(UHB), and the Mott gap will be significantly diminished. Combined with the Cl defect and the Rb adatom/cluster results, the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. Our results provide information to understand the electron doping to the parent compound of cuprates.

The influence of boundary conditions on the distribution of energetic electrons during collisionless magnetic reconnection

We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary(PB) and fully-opened boundary(OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.

The anisotropy of suprathermal electrons in the Martian ionosphere

Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth investigation of the pitch angle distribution of suprathermal electrons at two representative energies, 19−55 eV and 124−356 eV, using the extensive measurements made by the Solar Wind Electron Analyzer on board the Mars Atmosphere and Volatile Evolution. Throughout the study, we focus on the overall degree of anisotropy, defined as the standard deviation of suprathermal electron intensity among different directions which is normalized by the mean omni-directional intensity. The available data reveal the following characteristics: (1) In general, low energy electrons are more isotropic than high energy electrons, and dayside electrons are more isotropic than nightside electrons;(2) On the dayside, the anisotropy increases with increasing altitude at low energies but remains roughly constant at high energies, whereas on the nightside, the anisotropy decreases with increasing altitude at all energies;(3) Electrons tend to be more isotropic in strongly magnetized regions than in weakly magnetized regions, especially on the nightside. These observations indicate that the anisotropy is a useful diagnostic of suprathermal electron transport, for which the conversion between the parallel and perpendicular momenta as required by the conservation of the first adiabatic invariant, along with the atmospheric absorption at low altitudes, are two crucial factors modulating the observed variation of the anisotropy. Our analysis also highlights the different roles on the observed anisotropy exerted by suprathermal electrons of different origins.

Re-delocalization of localized d-electrons in VO_(2)(R)-VS_(4)hetero-structure enables high performance of rechargeable Mg-ion batteries

Rechargeable Mg-ion batteries(MIBs)have attracted much more attentions by virtue of the high capacity from the two electrons chemistry.However,the reversible Mg^(2+)diffusion in cathode materials is restricted by the strong interactions between the high-polarized bivalent Mg^(2+)ions and anionic lattice.Herein,we design and propose a hetero-structural VO_(2)(R)-VS_(4)cathode,in which the re-delocalized d-electrons can effectively shield the polarity of Mg^(2+)ions.Theoretically,the electrons should spontaneously transfer from VS_(4)to VO_(2)(R)through the interfaces of hetero-structure due to the lower work function value of VS_(4).Furthermore,the internal electrons transfer lead to the electronic injection into VO_(2)(R)from VS_(4)and the partially broken V-V dimers,indicating the presence of lone pair electrons and charge re-delocalization.Benefiting from the shield effect of re-delocalized electrons,and the weakened attraction between cations and O/S anions enables more S^(2-)-S_(2)^(2-)redox groups to participate the electrochemical reactions and compensate the double charge of Mg^(2+)ions.Accordingly,VO_(2)(R)-VS_(4)hetero-structure exhibits a high specific capacity of 554 mA h g^(-1)at 50 mA g^(-1).It is believed that the charge re-delocalization of cathode extremely boost the Mg^(2+)ions migration for the high-capacity of MIBs.

A statistical analysis of the Kappa-type energy spectrum distribution of radiation belt electrons observed by Van Allen Probes

The energy spectrum of energetic electrons is a key factor representing the dynamic variations of Earth’s Van Allen radiation belts.Increased measurements have indicated that the commonly used Maxwellian and Kappa distributions are inadequate for capturing the realistic spectral distributions of radiation belt electrons.Here we adopt the Kappa-type(KT)distribution as the fitting function and perform a statistical analysis to investigate the radiation belt electron flux spectra observed by the Van Allen Probes.By calculating the optimal values of the key KT distribution parameters(i.e.,κandθ2)from the observed spectral shapes,we fit the radiation belt electron fluxes at different L-shells under different geomagnetic conditions.In this manner,we obtain typical values of the KT distribution parameters,which are statistically feasible for modeling the radiation belt electron flux profiles during either geomagnetically quiet or active periods.A comparison of the KT distribution model results with those using the Maxwellian or Kappa distribution reveals the advantage of the KT distribution for studying the overall properties of the radiation belt electron spectral distribution,which has important implications for deepening the current understanding of the radiation belt electron dynamics under evolving geomagnetic conditions.

The Lone Pair Electrons in Post-Transition Metal and Their Contribution to Optical Response

The stereochemically active lone pairs around post-transition metal atoms play an important role in determining distorted lattice structure and optical response.The lone pair electrons are characterized by crystal orbitals,electron localization function(ELF)and partial density of states(PDOS).Birefringence is evaluated by means of a Born effective charge approach based on modern polarization theory.The origin of the different responses of birefringence and second-harmonic generation(SHG)is explored,as well as the effect of spin-orbit coupling(SOC)on the band structure and optical properties is explored.The study of this paper can help to deeply understand the lone pairs and their contribution to optical property.

Electrically-driven ultrafast out-of-equilibrium light emission from hot electrons in suspended graphene/hBN heterostructures

Nanoscale light sources with high speed of electrical modulation and low energy consumption are key components for nanophotonics and optoelectronics.The record-high carrier mobility and ultrafast carrier dynamics of graphene make it promising as an atomically thin light emitter which can be further integrated into arbitrary platforms by van der Waals forces.However,due to the zero bandgap,graphene is difficult to emit light through the interband recombination of carriers like conventional semiconductors.Here,we demonstrate ultrafast thermal light emitters based on suspended graphene/hexagonal boron nitride(Gr/hBN)heterostructures.Electrons in biased graphene are significantly heated up to 2800 K at modest electric fields,emitting bright photons from the near-infrared to the visible spectral range.By eliminating the heat dissipation channel of the substrate,the radiation efficiency of the suspended Gr/hBN device is about two orders of magnitude greater than that of graphene devices supported on SiO2or hBN.Wefurther demonstrate that hot electrons and low-energy acoustic phonons in graphene are weakly coupled to each other and are not in full thermal equilibrium.Direct cooling ofhigh-temperature hot electrons to low-temperature acoustic phonons is enabled by the significant near-field heat transfer at the highly localized Gr/hBN interface,resulting in ultrafast thermal emission with up to 1 GHz bandwidth under electrical excitation.It is found thatsuspending the Gr/hBN heterostructures on the SiO2trenches significantly modifies the light emission due to the formation of the optical cavity and showed a~440%enhancement inintensity at the peak wavelength of 940 nm compared to the black-body thermal radiation.The demonstration of electrically driven ultrafast light emission from suspended Gr/hBNheterostructures sheds the light on applications of graphene heterostructures in photonicintegrated circuits,such as broadband light sources and ultrafast thermo-optic phase modulators.

Application of the HSAB principle for the quantitative analysis of nucleophilicity/basicity of organic compounds with lone-pair electrons

Based on the density functional theory,we described here a method to investigate the quantitative relationship between nucleophilicity/basicity and HSAB-theory-based properties of compounds with lone-pair electrons.Descriptors including global softness,Fukui function,local softness and local mulliken charge were calculated at SVWN/DN~* level of DFT with PC Spartan Pro.Nucleophilicity and basicity of 28 selected compounds were classified based on intensity.BP algorithm of artificial neural network(ANN) was employed to study the relationship between the descriptors and nucleophilicity/basicity.Cross-validation was carried out to avoid the over-fitting in training of ANN.A BP network was trained to quantify the relationship between HSAB-theory-based properties and nucleophilicity/basicity of compounds with lone-pair electrons.The results show that the prediction based on the network matches with the experimental results well.The local softness and Fukui function have a better relationship with nucleophilicity and local mulliken charge than with the basicity.The trained BP network could be utilized for predicting the nucleophilicity/basicity of compounds or functional groups with lone-pair electrons.

Application of the HSAB principle for the quantitative analysis of nucleophilicity/basicity of organic compounds with lone-pair electrons

Based on the density functional theory, we described here a method to investigate the quantitative relationship between nucleophilicity/basicity and HSAB-theory-based properties of compounds with lone-pair electrons. Descriptors including global softness, Fukui function, local softness and local mulliken charge were calculated at SVWN/DN＊ level of DFT with PC Spartan Pro. Nucleophilicity and basicity of 28 selected compounds were classified based on intensity. BP algorithm of artificial neural network （ANN） was employed to study the relationship between the descriptors and nucleophilicity/basicity. Cross-validation was carried out to avoid the over-fitting in training of ANN. A BP network was trained to quantify the relationship between HSAB-theory-based properties and nucleophilicity/basicity of compounds with lone-pair electrons. The results show that the prediction based on the network matches with the experimental results well. The local softness and Fukui function have a better relationship with nucleophilicity and local mulliken charge than with the basicity. The trained BP network could be utilized for predicting the nucleophilicity/basicity of compounds or functional groups with lone-pair electrons.

A Generic Strategy to Create Mechanically Interlocked Nanocomposite/Hydrogel Hybrid Electrodes for Epidermal Electronics

Stretchable electronics are crucial enablers for next-generation wearables intimately integrated into the human body.As the primary compliant conductors used in these devices,metallic nanostructure/elastomer composites often struggle to form conformal contact with the textured skin.Hybrid electrodes have been consequently developed based on conductive nanocomposite and soft hydrogels to establish seamless skin-device interfaces.However,chemical modifications are typically needed for reliable bonding,which can alter their original properties.To overcome this limitation,this study presents a facile fabrication approach for mechanically interlocked nanocomposite/hydrogel hybrid electrodes.In this physical process,soft microfoams are thermally laminated on silver nanowire nanocomposites as a porous interface,which forms an interpenetrating network with the hydrogel.The microfoam-enabled bonding strategy is generally compatible with various polymers.The resulting interlocked hybrids have a 28-fold improved interfacial toughness compared to directly stacked hybrids.These electrodes achieve firm attachment to the skin and low contact impedance using tissue-adhesive hydrogels.They have been successfully integrated into an epidermal sleeve to distinguish hand gestures by sensing mus-cle contractions.Interlocked nanocomposite/hydrogel hybrids reported here offer a promising platform to combine the benefits of both materials for epidermal devices and systems.

Investigation on taste characteristics and sensory perception of soft-boiled chicken during oral processing based on electronic tongue and electronic nose

The sensory perception of food is a dynamic process,which is closely related to the release of flavor substances during oral processing.It’s not only affected by the food material,but also subjected to the individual oral environment.To explore the oral processing characteristics of soft-boiled chicken,the sensory properties,texture,particle size,viscosity,characteristic values of electronic nose and tongue of different chicken samples were investigated.The correlation analysis showed that the physical characteristics especially the cohesiveness,springiness,resilience of the sample determined oral processing behavior.The addition of chicken skin played a role in lubrication during oral processing.The particle size of the bolus was heightened at the early stage,and the fluidity was enhanced in the end,which reduced the chewing time to the swallowing point and raised the aromatic compounds signal of electronic nose.But the effect of chicken skin on chicken thigh with relatively high fat content,was opposite in electronic nose,which had a certain masking effect on the perception of umami and sweet taste.In conclusion,fat played a critical role in chicken oral processing and chicken thigh had obvious advantages in comprehensive evaluation of soft-boiled chicken,which was more popular among people.

Secondary electron emission and photoemission from a negative electron affinity semiconductor with large mean escape depth of excited electrons

The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the maximumδandδat 100.0 keV≥E_(po)≥1.0 keV of a NEASLD with the deduced formulae are presented(B is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter,δis the secondary electron yield,E_(po)is the incident energy of primary electrons and E_(pom)is the E_(po)corresponding to the maximumδ).The parameters obtained here are analyzed,and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors.The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated,and it is concluded that the presented method of obtaining A is more accurate than that of obtaining the corresponding parameter for a NEAS with largeλ_(ph)(λ_(ph)being the mean escape depth of photoelectrons),and that the presented method of calculating B at E_(po)>10.0 keV is more widely applicable for obtaining the corresponding parameters for a NEAS with largeλ_(ph).

Sweat-permeable electronic patches by designing threedimensional liquid diodes

Wearable electronics face a significant challenge related to the limited permeability of electronic materials/devices.This issue results in sweat accumulation across the interface of the device and skin following a specific period of use[1−3].Not only does it bring about discomfort for users regarding thermos-physiology,but it also has a detrimental effect on interface adhesion and signal quality,thus hindering exact sig-nal monitoring during prolonged periods[4−6].

3D‑Printed Carbon‑Based Conformal Electromagnetic Interference Shielding Module for Integrated Electronics

Electromagnetic interference shielding(EMI SE)modules are the core com-ponent of modern electronics.However,the tra-ditional metal-based SE modules always take up indispensable three-dimensional space inside electronics,posing a major obstacle to the integra-tion of electronics.The innovation of integrating 3D-printed conformal shielding(c-SE)modules with packaging materials onto core electronics offers infinite possibilities to satisfy ideal SE func-tion without occupying additional space.Herein,the 3D printable carbon-based inks with various proportions of graphene and carbon nanotube nanoparticles are well-formulated by manipulating their rheological peculiarity.Accordingly,the free-constructed architectures with arbitrarily-customized structure and multifunctionality are created via 3D printing.In particular,the SE performance of 3D-printed frame is up to 61.4 dB,simultaneously accompanied with an ultralight architecture of 0.076 g cm^(-3) and a superhigh specific shielding of 802.4 dB cm3 g^(-1).Moreover,as a proof-of-concept,the 3D-printed c-SE module is in situ integrated into core electronics,successfully replacing the traditional metal-based module to afford multiple functions for electromagnetic compatibility and thermal dissipa-tion.Thus,this scientific innovation completely makes up the blank for assembling carbon-based c-SE modules and sheds a brilliant light on developing the next generation of high-performance shielding materials with arbitrarily-customized structure for integrated electronics.

An Environment‑Tolerant Ion‑Conducting Double‑Network Composite Hydrogel for High‑Performance Flexible Electronic Devices

High-performance ion-conducting hydrogels(ICHs)are vital for developing flexible electronic devices.However,the robustness and ion-conducting behavior of ICHs deteriorate at extreme tempera-tures,hampering their use in soft electronics.To resolve these issues,a method involving freeze–thawing and ionizing radiation technology is reported herein for synthesizing a novel double-network(DN)ICH based on a poly(ionic liquid)/MXene/poly(vinyl alcohol)(PMP DN ICH)system.The well-designed ICH exhibits outstanding ionic conductivity(63.89 mS cm^(-1) at 25℃),excellent temperature resistance(-60–80℃),prolonged stability(30 d at ambient temperature),high oxidation resist-ance,remarkable antibacterial activity,decent mechanical performance,and adhesion.Additionally,the ICH performs effectively in a flexible wireless strain sensor,thermal sensor,all-solid-state supercapacitor,and single-electrode triboelectric nanogenerator,thereby highlighting its viability in constructing soft electronic devices.The highly integrated gel structure endows these flexible electronic devices with stable,reliable signal output performance.In particular,the all-solid-state supercapacitor containing the PMP DN ICH electrolyte exhibits a high areal specific capacitance of 253.38 mF cm^(-2)(current density,1 mA cm^(-2))and excellent environmental adaptability.This study paves the way for the design and fabrication of high-performance mul-tifunctional/flexible ICHs for wearable sensing,energy-storage,and energy-harvesting applications.

A refined Monte Carlo code for low-energy electron emission from gold material irradiated with sub-keV electrons

Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.

Valence electronic engineering of superhydrophilic Dy-evoked Ni-MOF outperforming RuO_(2) for highly efficient electrocatalytic oxygen evolution

Tackling the problem of poor conductivity and catalytic stability of pristine metal-organic frameworks(MOFs) is crucial to improve their oxygen evolution reaction(OER) performance.Herein,we introduce a novel strategy of dysprosium(Dy) doping,using the unique 4f orbitals of this rare earth element to enhance electrocatalytic activity of MOFs.Our method involves constructing Dy-doped Ni-MOF(Dy@Ni-MOF) nanoneedles on carbon cloth via a Dy-induced valence electronic perturbation approach.Experiments and density functional theory(DFT) calculations reveal that Dy doping can effectively modify the electronic structure of the Ni active centers and foster a strong electronic interaction between Ni and Dy.The resulting benefits include a reduced work function and a closer proximity of the d-band center to the Fermi level,which is conducive to improving electrical conductivity and promoting the adsorption of oxygen-containing intermediates.Furthermore,the Dy@Ni-MOF achieves superhydrophilicity,ensuring effective electrolyte contact and thus accelerating reaction kinetics,Ex-situ and in-situ analysis results manifest Dy_(2)O_(3)/NiOOH as the actual active species.Therefore,Dy@Ni-MOF shows impressive OER performance,significantly surpassing Ni-MOF.Besides,the overall water splitting device with Dy@NiMOF as an anode delivers a low cell voltage of 1.51 V at 10 mA cm^(-2) and demonstrates long-term stability for 100 h,positioning it as a promising substitute for precious metal catalysts.

Effect of tearing modes on the confinement of runaway electrons in Experimental Advanced Superconducting Tokamak

The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)Dr is derived based on the time response relation between the tearing modes and runaway electrons.The results indicate that,the magnetic fluctuations of tearing modes will enhance the radial diffusion of runaway electrons when the magnetic island is small.Following the increasing of the magnetic fluctuations of the tearing modes,the formed large magnetic island may weaken the radial diffusion of runaway electrons.The results can be important to understand the confinement of runaway electrons when large magnetic islands exist in the plasma.

Laboratory observation of electron energy distribution near three-dimensional magnetic nulls

The acceleration of electrons near three-dimensional(3D)magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process.To explore electron acceleration in a 3D magnetic null topology,we constructed a pair of 3D magnetic nulls in the PKU Plasma Test(PPT)device and observed acceleration of electrons near magnetic nulls.This study measured the plasma floating potential and ion density profiles around the 3D magnetic null.The potential wells near nulls may be related to the energy variations of electrons,so we measured the electron distribution functions(EDFs)at different spatial positions.The axial variation of EDF shows that the electrons deviate from the Maxwell distribution near magnetic nulls.With scanning probes that can directionally measure and theoretically analyze based on curve fitting,the variations of EDFs are linked to the changes of plasma potential under 3D magnetic null topology.The kinetic energy of electrons accelerated by the electric field is 6 eV(v_(e)~7v_(Alfvén-e))and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.