The propagation properties of ion-acoustic solitary and shock waves in the magnetized viscous plasma with nonthermal trapped electrons are investigated.The Cairns-Gurevich distribution as the electron distribution is ...The propagation properties of ion-acoustic solitary and shock waves in the magnetized viscous plasma with nonthermal trapped electrons are investigated.The Cairns-Gurevich distribution as the electron distribution is considered to describe the plasma nonthermality and particle trapping.By adopting the reductive perturbation technique,we derived the nonlinear Schamel-Korteweg-de Vries-Burgers(SKdVB)equation,and then obtained the ion-acoustic shock and solitary wave solutions of the SKdVB equation for different limiting cases.It is found that the impact of nonthermal parameterα,external magnetic fieldΩ,obliqueness lz,wave speed U0,and the ion kinematic viscosityη0can significantly change the characteristics of the shock and solitary waves.These results may be useful for better understanding the propagation of nonlinear structures in space(i.e.Earth's magnetosphere and ionosphere,auroral regions)and laboratory plasma with nonthermal trapped electrons.展开更多
The discovery of pressure-induced superconducting electrides has sparked a intense wave of interest in novel superconductors.However,opinions vary regarding the relationship between non-nuclear attractors(NNAs)and sup...The discovery of pressure-induced superconducting electrides has sparked a intense wave of interest in novel superconductors.However,opinions vary regarding the relationship between non-nuclear attractors(NNAs)and superconductivity,with two opposing views currently represented by the materials Li_(6)P and Li_(6)C.Here,we choose the ternary Li–C–P as a model system and reveal the underlying mechanism by which NNAs contribute to superconductivity.The loosely bound NNAs in the superlithide Li_(14)CP covalently bond with Li and form unique satellite interstitial electrons(SIEs)around Li near the Fermi level,dominating the superconductivity.First-principles calculations show that the SIEs progressively increase in number and couple strongly with phonons at high pressure.Moreover,the Fermi surface nesting associated with SIEs induces phonon softening,further enhancing the electron–phonon coupling and giving the superlithide Li_(14)CP a T_(c)of 10.6 K at 300 GPa.The leading role of SIEs in superconductivity is a general one and is also relevant to the recently predicted Li_(6)P and Li_(6)C.Our work presented here reshapes the understanding of NNA-dominated superconductivity and holds promise for guiding future discoveries and designs of novel high-temperature superconductors.展开更多
The triple bond in N_(2)has an extremely high bond energy and is thus difficult to break.N_(2)is commonly converted into NH3 artificially via the Haber-Bosch process,and NH_(3)can be utilized to produce other nitrogen...The triple bond in N_(2)has an extremely high bond energy and is thus difficult to break.N_(2)is commonly converted into NH3 artificially via the Haber-Bosch process,and NH_(3)can be utilized to produce other nitrogen-containing chemicals.Here,we developed an electron catalyzed method to directly fix N_(2)into azos,by pushing and pulling the electron into and from the aromatic halide with the cyclic voltammetry method.The round-trip journey of electron can successfully weaken the triple bond in N_(2)through the electron pushing-induced aryl radical via a“brick trowel”transition state,and then produce the diazonium ions by pulling the electron out from the diazo radical intermediate.Different azos can be synthesized with this developed electron catalyzed approach.This approach provides a novel concept and practical route for the fixation of N_(2)at atmospheric pressure into chemical products valuable for industrial and commercial applications.展开更多
We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group e...We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group electronegativity, and atomic charge. The ionization potential of alkanes and mono-substituted alkanes, the chemical shift of 1H NMR, and the gas phase proton affinity of aliphatic amines, alcohols, and ethers were estimated. All the expressions have good correlations. Moreover, the Sanderson method and Bratsch method were modified on the basis of the valence electrons equilibration theory. The modified Sanderson method and modified Bratsch method are more effective than their original methods to estimate these properties.展开更多
The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut ...The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut within a {100} growth layer, and irradiated with 2 MeV electrons along the <100> axis. PL spectra of sample were collected under 532 nm and 355 nm laser excitation, at room temperature and 77 K, and linear scanning analysis along incident depth was applied to determine the distribution of defects. The pre-irradiation characterization results revealed uniformly distributed PL centers at 389 nm, 469 nm, 533 nm, 575 nm (ZPL of NV 0), 637 nm (ZPL of NV -), and 736.7/737.1 nm (ZPL doublet of SiV -). After irradiation, the differential responses of these as-grown defects were observed, alongside the emergence of irradiation-induced defects, namely 489 nm center, H3 center (ZPL at 504 nm) and GR1 center (ZPL at 741 nm). The maximum penetration depth of 2 MeV electron-irradiation induced defects was determined to be 2.1 mm. This work primarily presents the depth profiles of both as-grown and irradiation-induced defects in 2 MeV electrons irradiated diamond. The result provides experimental data for better understanding of the radiation effect in diamonds. Serving as a reference for diamond enhancement by electron irradiation.展开更多
The gold nano-plates(Au NPLs)have been extensively studied for their high quality factor as mechanical resonators.But it remains still unclear how the thickness and morphology of Au NPLs affect the hot electron diffus...The gold nano-plates(Au NPLs)have been extensively studied for their high quality factor as mechanical resonators.But it remains still unclear how the thickness and morphology of Au NPLs affect the hot electron diffusion.Here we have employed transient absorption microscopy to gain spatiotemporal imaging of the hot electron diffusion in Au NPLs.Au NPLs of varying thickness over 200 nm were synthesized.It was found that the hot electron diffusion of Au NPL excited at the boundary is obviously faster than that excited at the internal surface.And thinner Au NPLs exhibit a faster hot electron diffusion rate compared to thicker Au NPLs.Because the time constant of hot electron cooling(electron-phonon coupling)is independent of the excited position and thickness of Au NPLs,the effect of electron-phonon coupling on hot electron diffusion should be ruled out.So the hot electron diffusion rate is highly dimensionality-dependent.The quasi-one-dimensional diffusion along the boundary of nanoplate has the fastest rate of 50 cm^(2)/s,and the three-dimensional diffusion has the slowest rate of 22 cm^(2)/s.The fundamental investigation on the hot electrons transport property of Au NPLs offers a new insight for designing metal-based optoelectronic devices.展开更多
The susceptibility of Pt catalyst surfaces to carbon monoxide(CO)poisoning in anodic hydrogen oxidation reaction(HOR)has been a critical constraint on the development of proton exchange membrane fuel cells(PEMFCs).Eff...The susceptibility of Pt catalyst surfaces to carbon monoxide(CO)poisoning in anodic hydrogen oxidation reaction(HOR)has been a critical constraint on the development of proton exchange membrane fuel cells(PEMFCs).Effectively regulating the electronic structure of Pt to enhance CO resistance is crucial for developing high-performance catalysts with robust anti-poisoning capabilities.Herein,the Pt/W@NCNF featured by Pt nanoparticles and atomical dispersed tungsten(W)sites on N-doped carbon nanofibers is developed for CO tolerance HOR catalyst.The presence of W enables the electron transfer from Pt,which promotes electron rearrangement in the Pt-5d orbitals.It not only optimizes the adsorption of H^(*) and CO^(*)on Pt,but also the OH^(*) intermediates adsorbed on the W sites oxidize the CO*adsorbed on Pt,thereby retaining more active sites for H_(2) adsorption and oxidation.The HOR exchange current density of Pt/W@NCNF reaches 1.35 times that of commercial Pt/C,and the limiting current density decreases by only 3.4%after introducing 1000 ppm CO in H_(2).Notably,the Pt/W@NCNF-based PEMFCs deliver markedly superior performance across a range of CO concentrations.The present study demonstrates that electronic modulation of Pt is an effective strategy for simultaneously achieving resistance to CO and promoted HOR activity.展开更多
In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty （complex） plasma are investigated. The dynamic of electrons is simu...In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty （complex） plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian （k） distribution function （DF）. The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique （RPT） a nonlinear modified Korteweg-de Vries （mKdV） equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively （or positively） charged. The properties of dust acoustic solitons （DASs） are also investigated numerically.展开更多
We present a coaxial detection of the backscattered electrons in SEM. The lens-aperture has been used to filter in energy and focus the backscattered electrons. This particular geometry allows us to eliminate the low ...We present a coaxial detection of the backscattered electrons in SEM. The lens-aperture has been used to filter in energy and focus the backscattered electrons. This particular geometry allows us to eliminate the low energy backscattered electrons and collect the backscattered electrons, which are backscattered close to the incident beam orientation. The main advantage of this geometry is adapted to topographic contrast attenuation and atomic number contrast enhancement. Thus this new SEM is very suitable to analyze the material composition.展开更多
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.De...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.展开更多
The important features of the rescattering trajectories in strong field ionization process such as the cutoff of the return energy at 3.17Up and that of the final energy at 10Up are obtained, based on the adiabatic ap...The important features of the rescattering trajectories in strong field ionization process such as the cutoff of the return energy at 3.17Up and that of the final energy at 10Up are obtained, based on the adiabatic approximation in which the initial momentum of the electron is assumed to be zero. We theoretically study the nonadiabatic effect by assuming a nonzero initial momentum on the rescattering trajectories based on the semiclassical simpleman model. We show that the nonzero initial momentum will modify both the maximal return energy at collision and the final energy after backward scattering, but in different ways for odd and even number of return trajectories. The energies are increased for even number of returns but are decreased for odd number of returns when the nonzero （positive or negative） initial momentum is applied.展开更多
The pursuit of high energy density has promoted the development of high-performance lithium metal batteries(LMBs).However,the underestimated but non-negligible dendrites of Li anode have been observed to shorten batte...The pursuit of high energy density has promoted the development of high-performance lithium metal batteries(LMBs).However,the underestimated but non-negligible dendrites of Li anode have been observed to shorten battery lifespan.Herein,a composite separator(TiO_(2-x)@PP),in which TiO_(2)with electron-localized oxygen vacancies(TiO_(2-x))is coated on a commercial PP separator,is fabricated to homogenize lithium ion transport and stabilize the lithium anode interface.With the utilization of TiO_(2-x)@PP separators,the symmetric lithium metal battery displays enhanced cycle stability over 800 h under a high current density of 8 m A cm^(-2).Moreover,the LMBs assembled with high-loading LiFePO_(4)(9.24 mg cm^(-2))deliver a stable cycling performance over 900 cycles at a rate of 0.5 C.Comprehensive theoretical studies based on density functional theory(DFT)further unveil the mechanism.The favorable TiO_(2-x)is beneficial for facilitating fast Li+migration and impeding anions transfer.In addressing the Li dendrite issues,the use of TiO_(2-x)@PP separator potentially provides a facile and attractive strategy for designing well-performing LMBs,which are expected to meet the application requirements of rechargeable batteries.展开更多
The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s...The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.展开更多
In this paper,we analyze one reconnection event observed by the Magnetospheric Multiscale(MMS)mission at the earth’s magnetopause.In this event,the spacecraft crossed the reconnection current sheet from the magnetosp...In this paper,we analyze one reconnection event observed by the Magnetospheric Multiscale(MMS)mission at the earth’s magnetopause.In this event,the spacecraft crossed the reconnection current sheet from the magnetospheric side to the magnetosheath side,and whistler waves were observed on both the magnetospheric and magnetosheath sides.On the magnetospheric side,the whistler waves propagated quasi-parallel to the magnetic field and toward the X-line,while on the magnetosheath side they propagated almost anti-parallel to the magnetic field and away from the X-line.Associated with the enhancement of the whistler waves,we find that the fluxes of energetic electrons are concentrated around the pitch angle 90°when their energies are higher than the minimum energy that is necessary for the resonant interactions between the energetic electrons and whistler waves.This observation provides in situ observational evidence of resonant interactions between energetic electrons and whistler waves in the magnetic reconnection.展开更多
We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot e...We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot electrons in ionized targets,using appropriate scattering differential cross sections with free plasma electrons and ionized or partially ionized atoms.In this paper,we show that a target in the plasma state stops and diffuses electrons more effectively than a cold target(i.e.,a target under standard conditions in which ionization is absent).This is related to the fact that in a plasma,the nuclear potential of plasma nuclei has a greater range than in the cold case,where the screening distance is determined by the electronic structure of atoms.However,in the ablation zone created by laser interaction,electrons undergo less severe scattering,counterbalancing the enhanced diffusion that occurs in the bulk.We also show that hard collisions,i.e.,collisions with large polar scattering angle,play a primary role in electron beam diffusion and should not be neglected.An application of the plasma MonteCarlo model to typical shock ignition implosions suggests that hot electrons will not give rise to any preheating concerns if their Maxwellian temperature is lower than 25–30 keV,although the presence of populations at higher temperatures must be suppressed.This result does not depend strongly on the initial angular divergence of the electron beam set in the simulations.展开更多
Previous studies have shown that leak electro ns in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the exit.In this paper,a onedimensional fluid model is built ...Previous studies have shown that leak electro ns in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the exit.In this paper,a onedimensional fluid model is built along two typical electron paths to study the influence of leak electrons on the discharge characteristics of a cusped field thruster,considering the electron temperature equation.It is found that the frequencies of low-frequency oscillations increase with a decrease in the proportion of leak electrons,which is related to an increase in the ion speed in the channel.Simulation results show that the position of the peak electron temperature is near the magnetic cusp on the exit and the position of the peak electron density is located downstream from the middle magnetic tip.With a decrease in the proportion of the leak electrons,the peak electron temperature and peak electron density decrease and the position of the peak electron density moves away from the exit,which is related to a decrease in the potential fall on the exit and an increase in confinement of electrons to the middle magnetic cusp.展开更多
We demonstrated the interaction of a gold cone target with a femto second（fs） laser pulse above the relativistic intensity of 1.37×10 18 μm 2 W/cm 2.Relativistic electrons with energy above 2 MeV were observed...We demonstrated the interaction of a gold cone target with a femto second（fs） laser pulse above the relativistic intensity of 1.37×10 18 μm 2 W/cm 2.Relativistic electrons with energy above 2 MeV were observed.A 25%-40% increase of the electron temperature is achieved compared to the case when a plane gold target is used.The electron temperature increase results from the guiding of the laser beam at the tip and the intense quasistatic magnetic field in the cone geometry.The behavior of the relativistic electrons is verified in our 2D-PIC simulations.展开更多
The basic properties of dust-ion-acoustic （DIA） shock waves in an unmagnetized dusty plasma （containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dus...The basic properties of dust-ion-acoustic （DIA） shock waves in an unmagnetized dusty plasma （containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains） are investi- gated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.展开更多
The formation of runaway electron pre-ionized diffuse discharges at the pressures 0.05-0.7 MPa of in air, argon, nitrogen, and SF6 in an inhomogeneous electric field was investigated. Dynamics of intensity of the disc...The formation of runaway electron pre-ionized diffuse discharges at the pressures 0.05-0.7 MPa of in air, argon, nitrogen, and SF6 in an inhomogeneous electric field was investigated. Dynamics of intensity of the discharge plasma radiation from the different discharge gap regions in the gas pressure range （0.05-0.7 MPa） was established. It was shown that, the breakdown is occurred owing to the ionization wave, which starts from the electrode with small radius of curvature at both polarity of high voltage pulses. It is seen that formation of bright spots on the fiat electrode at the negative polarity of the electrode with small radius of curvature are observed during the changing of the discharge current polarity. It was shown that, at positive polarity of electrode with a small radius of curvature, the bright spots on the flat electrode arise due to the participation of the dynamic displacement current in the gap conductance.展开更多
A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and...A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.展开更多
文摘The propagation properties of ion-acoustic solitary and shock waves in the magnetized viscous plasma with nonthermal trapped electrons are investigated.The Cairns-Gurevich distribution as the electron distribution is considered to describe the plasma nonthermality and particle trapping.By adopting the reductive perturbation technique,we derived the nonlinear Schamel-Korteweg-de Vries-Burgers(SKdVB)equation,and then obtained the ion-acoustic shock and solitary wave solutions of the SKdVB equation for different limiting cases.It is found that the impact of nonthermal parameterα,external magnetic fieldΩ,obliqueness lz,wave speed U0,and the ion kinematic viscosityη0can significantly change the characteristics of the shock and solitary waves.These results may be useful for better understanding the propagation of nonlinear structures in space(i.e.Earth's magnetosphere and ionosphere,auroral regions)and laboratory plasma with nonthermal trapped electrons.
基金supported by the National Key R&D Program of China(Grant No.2023YFA1406200)the National Natural Science Foundation of China(Grant Nos.12374004 and 12174141)the High Performance Computing Center of Jilin University,China。
文摘The discovery of pressure-induced superconducting electrides has sparked a intense wave of interest in novel superconductors.However,opinions vary regarding the relationship between non-nuclear attractors(NNAs)and superconductivity,with two opposing views currently represented by the materials Li_(6)P and Li_(6)C.Here,we choose the ternary Li–C–P as a model system and reveal the underlying mechanism by which NNAs contribute to superconductivity.The loosely bound NNAs in the superlithide Li_(14)CP covalently bond with Li and form unique satellite interstitial electrons(SIEs)around Li near the Fermi level,dominating the superconductivity.First-principles calculations show that the SIEs progressively increase in number and couple strongly with phonons at high pressure.Moreover,the Fermi surface nesting associated with SIEs induces phonon softening,further enhancing the electron–phonon coupling and giving the superlithide Li_(14)CP a T_(c)of 10.6 K at 300 GPa.The leading role of SIEs in superconductivity is a general one and is also relevant to the recently predicted Li_(6)P and Li_(6)C.Our work presented here reshapes the understanding of NNA-dominated superconductivity and holds promise for guiding future discoveries and designs of novel high-temperature superconductors.
文摘The triple bond in N_(2)has an extremely high bond energy and is thus difficult to break.N_(2)is commonly converted into NH3 artificially via the Haber-Bosch process,and NH_(3)can be utilized to produce other nitrogen-containing chemicals.Here,we developed an electron catalyzed method to directly fix N_(2)into azos,by pushing and pulling the electron into and from the aromatic halide with the cyclic voltammetry method.The round-trip journey of electron can successfully weaken the triple bond in N_(2)through the electron pushing-induced aryl radical via a“brick trowel”transition state,and then produce the diazonium ions by pulling the electron out from the diazo radical intermediate.Different azos can be synthesized with this developed electron catalyzed approach.This approach provides a novel concept and practical route for the fixation of N_(2)at atmospheric pressure into chemical products valuable for industrial and commercial applications.
文摘We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group electronegativity, and atomic charge. The ionization potential of alkanes and mono-substituted alkanes, the chemical shift of 1H NMR, and the gas phase proton affinity of aliphatic amines, alcohols, and ethers were estimated. All the expressions have good correlations. Moreover, the Sanderson method and Bratsch method were modified on the basis of the valence electrons equilibration theory. The modified Sanderson method and modified Bratsch method are more effective than their original methods to estimate these properties.
基金This work is supported by National Natural Science Foundation of China(No.42372054)。
文摘The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut within a {100} growth layer, and irradiated with 2 MeV electrons along the <100> axis. PL spectra of sample were collected under 532 nm and 355 nm laser excitation, at room temperature and 77 K, and linear scanning analysis along incident depth was applied to determine the distribution of defects. The pre-irradiation characterization results revealed uniformly distributed PL centers at 389 nm, 469 nm, 533 nm, 575 nm (ZPL of NV 0), 637 nm (ZPL of NV -), and 736.7/737.1 nm (ZPL doublet of SiV -). After irradiation, the differential responses of these as-grown defects were observed, alongside the emergence of irradiation-induced defects, namely 489 nm center, H3 center (ZPL at 504 nm) and GR1 center (ZPL at 741 nm). The maximum penetration depth of 2 MeV electron-irradiation induced defects was determined to be 2.1 mm. This work primarily presents the depth profiles of both as-grown and irradiation-induced defects in 2 MeV electrons irradiated diamond. The result provides experimental data for better understanding of the radiation effect in diamonds. Serving as a reference for diamond enhancement by electron irradiation.
基金supported by the National Natural Science Foundation of China(No.22273006).
文摘The gold nano-plates(Au NPLs)have been extensively studied for their high quality factor as mechanical resonators.But it remains still unclear how the thickness and morphology of Au NPLs affect the hot electron diffusion.Here we have employed transient absorption microscopy to gain spatiotemporal imaging of the hot electron diffusion in Au NPLs.Au NPLs of varying thickness over 200 nm were synthesized.It was found that the hot electron diffusion of Au NPL excited at the boundary is obviously faster than that excited at the internal surface.And thinner Au NPLs exhibit a faster hot electron diffusion rate compared to thicker Au NPLs.Because the time constant of hot electron cooling(electron-phonon coupling)is independent of the excited position and thickness of Au NPLs,the effect of electron-phonon coupling on hot electron diffusion should be ruled out.So the hot electron diffusion rate is highly dimensionality-dependent.The quasi-one-dimensional diffusion along the boundary of nanoplate has the fastest rate of 50 cm^(2)/s,and the three-dimensional diffusion has the slowest rate of 22 cm^(2)/s.The fundamental investigation on the hot electrons transport property of Au NPLs offers a new insight for designing metal-based optoelectronic devices.
基金supported by the National Natural Science Foundation of China(22179034,22279030)the Natural Science Foundation of Heilongjiang Province(ZD2023B002).
文摘The susceptibility of Pt catalyst surfaces to carbon monoxide(CO)poisoning in anodic hydrogen oxidation reaction(HOR)has been a critical constraint on the development of proton exchange membrane fuel cells(PEMFCs).Effectively regulating the electronic structure of Pt to enhance CO resistance is crucial for developing high-performance catalysts with robust anti-poisoning capabilities.Herein,the Pt/W@NCNF featured by Pt nanoparticles and atomical dispersed tungsten(W)sites on N-doped carbon nanofibers is developed for CO tolerance HOR catalyst.The presence of W enables the electron transfer from Pt,which promotes electron rearrangement in the Pt-5d orbitals.It not only optimizes the adsorption of H^(*) and CO^(*)on Pt,but also the OH^(*) intermediates adsorbed on the W sites oxidize the CO*adsorbed on Pt,thereby retaining more active sites for H_(2) adsorption and oxidation.The HOR exchange current density of Pt/W@NCNF reaches 1.35 times that of commercial Pt/C,and the limiting current density decreases by only 3.4%after introducing 1000 ppm CO in H_(2).Notably,the Pt/W@NCNF-based PEMFCs deliver markedly superior performance across a range of CO concentrations.The present study demonstrates that electronic modulation of Pt is an effective strategy for simultaneously achieving resistance to CO and promoted HOR activity.
文摘In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty （complex） plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian （k） distribution function （DF）. The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique （RPT） a nonlinear modified Korteweg-de Vries （mKdV） equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively （or positively） charged. The properties of dust acoustic solitons （DASs） are also investigated numerically.
基金the National Natural Science Foundation of China!10045001
文摘We present a coaxial detection of the backscattered electrons in SEM. The lens-aperture has been used to filter in energy and focus the backscattered electrons. This particular geometry allows us to eliminate the low energy backscattered electrons and collect the backscattered electrons, which are backscattered close to the incident beam orientation. The main advantage of this geometry is adapted to topographic contrast attenuation and atomic number contrast enhancement. Thus this new SEM is very suitable to analyze the material composition.
基金National Science & Technology Major Project of China(Grant No.2009ZX09501-002)National Natural Science Foundation of China(Grant No.20802006).
文摘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.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11425414 and 11504215the Scientific Research Training Program of Shanxi University
文摘The important features of the rescattering trajectories in strong field ionization process such as the cutoff of the return energy at 3.17Up and that of the final energy at 10Up are obtained, based on the adiabatic approximation in which the initial momentum of the electron is assumed to be zero. We theoretically study the nonadiabatic effect by assuming a nonzero initial momentum on the rescattering trajectories based on the semiclassical simpleman model. We show that the nonzero initial momentum will modify both the maximal return energy at collision and the final energy after backward scattering, but in different ways for odd and even number of return trajectories. The energies are increased for even number of returns but are decreased for odd number of returns when the nonzero （positive or negative） initial momentum is applied.
基金financial support provided by the National Natural Science Foundation of China(52064049)the Key National Natural Science Foundation of Yunnan Province(2018FA028 and 2019FY003023)+1 种基金the International Joint Research Center for Advanced Energy Materials of Yunnan Province(202003AE140001)the Key Laboratory of Solid State Ions for Green Energy of Yunnan University(2019),the Analysis and Measurements Center of Yunnan University for the sample testing service,and the Postgraduate Research and Innovation Foundation of Yunnan University(2021Y348)。
文摘The pursuit of high energy density has promoted the development of high-performance lithium metal batteries(LMBs).However,the underestimated but non-negligible dendrites of Li anode have been observed to shorten battery lifespan.Herein,a composite separator(TiO_(2-x)@PP),in which TiO_(2)with electron-localized oxygen vacancies(TiO_(2-x))is coated on a commercial PP separator,is fabricated to homogenize lithium ion transport and stabilize the lithium anode interface.With the utilization of TiO_(2-x)@PP separators,the symmetric lithium metal battery displays enhanced cycle stability over 800 h under a high current density of 8 m A cm^(-2).Moreover,the LMBs assembled with high-loading LiFePO_(4)(9.24 mg cm^(-2))deliver a stable cycling performance over 900 cycles at a rate of 0.5 C.Comprehensive theoretical studies based on density functional theory(DFT)further unveil the mechanism.The favorable TiO_(2-x)is beneficial for facilitating fast Li+migration and impeding anions transfer.In addressing the Li dendrite issues,the use of TiO_(2-x)@PP separator potentially provides a facile and attractive strategy for designing well-performing LMBs,which are expected to meet the application requirements of rechargeable batteries.
基金supported by the National Natural Science Foundation of China(51125009,91434118,21401185,21521092)Hundred Talents Program of Chinese Academy of SciencesJilin Province Science and Technology Development Project(20170101092JC,20160520006JH)
文摘The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.
基金supported by NSFC grants 41527804 and 41774169Key Research Program of Frontier Sciences, CAS(QYZDJ-SSW-DQC010)
文摘In this paper,we analyze one reconnection event observed by the Magnetospheric Multiscale(MMS)mission at the earth’s magnetopause.In this event,the spacecraft crossed the reconnection current sheet from the magnetospheric side to the magnetosheath side,and whistler waves were observed on both the magnetospheric and magnetosheath sides.On the magnetospheric side,the whistler waves propagated quasi-parallel to the magnetic field and toward the X-line,while on the magnetosheath side they propagated almost anti-parallel to the magnetic field and away from the X-line.Associated with the enhancement of the whistler waves,we find that the fluxes of energetic electrons are concentrated around the pitch angle 90°when their energies are higher than the minimum energy that is necessary for the resonant interactions between the energetic electrons and whistler waves.This observation provides in situ observational evidence of resonant interactions between energetic electrons and whistler waves in the magnetic reconnection.
基金This work has been carried out within the framework of the EUROfusion Enabling Research Project No.AWP17-ENR-IFECEA-01“Preparation and Realization of European Shock Ignition Experiments”and has received funding from the Euratom Research and Training Program 2014-2018 under Grant Agreement No.633053.The views and opinions expressed herein do not necessarily reflect those of the European Commission.
文摘We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot electrons in ionized targets,using appropriate scattering differential cross sections with free plasma electrons and ionized or partially ionized atoms.In this paper,we show that a target in the plasma state stops and diffuses electrons more effectively than a cold target(i.e.,a target under standard conditions in which ionization is absent).This is related to the fact that in a plasma,the nuclear potential of plasma nuclei has a greater range than in the cold case,where the screening distance is determined by the electronic structure of atoms.However,in the ablation zone created by laser interaction,electrons undergo less severe scattering,counterbalancing the enhanced diffusion that occurs in the bulk.We also show that hard collisions,i.e.,collisions with large polar scattering angle,play a primary role in electron beam diffusion and should not be neglected.An application of the plasma MonteCarlo model to typical shock ignition implosions suggests that hot electrons will not give rise to any preheating concerns if their Maxwellian temperature is lower than 25–30 keV,although the presence of populations at higher temperatures must be suppressed.This result does not depend strongly on the initial angular divergence of the electron beam set in the simulations.
文摘Previous studies have shown that leak electro ns in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the exit.In this paper,a onedimensional fluid model is built along two typical electron paths to study the influence of leak electrons on the discharge characteristics of a cusped field thruster,considering the electron temperature equation.It is found that the frequencies of low-frequency oscillations increase with a decrease in the proportion of leak electrons,which is related to an increase in the ion speed in the channel.Simulation results show that the position of the peak electron temperature is near the magnetic cusp on the exit and the position of the peak electron density is located downstream from the middle magnetic tip.With a decrease in the proportion of the leak electrons,the peak electron temperature and peak electron density decrease and the position of the peak electron density moves away from the exit,which is related to a decrease in the potential fall on the exit and an increase in confinement of electrons to the middle magnetic cusp.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10975121 and 11174259)the Foundation of National Key Laboratory of Plasma Physics
文摘We demonstrated the interaction of a gold cone target with a femto second（fs） laser pulse above the relativistic intensity of 1.37×10 18 μm 2 W/cm 2.Relativistic electrons with energy above 2 MeV were observed.A 25%-40% increase of the electron temperature is achieved compared to the case when a plane gold target is used.The electron temperature increase results from the guiding of the laser beam at the tip and the intense quasistatic magnetic field in the cone geometry.The behavior of the relativistic electrons is verified in our 2D-PIC simulations.
文摘The basic properties of dust-ion-acoustic （DIA） shock waves in an unmagnetized dusty plasma （containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains） are investi- gated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.
基金Acknowledgments The work was supported by the grant from the Russian Science Foundation, project No. 14-29-00052.
文摘The formation of runaway electron pre-ionized diffuse discharges at the pressures 0.05-0.7 MPa of in air, argon, nitrogen, and SF6 in an inhomogeneous electric field was investigated. Dynamics of intensity of the discharge plasma radiation from the different discharge gap regions in the gas pressure range （0.05-0.7 MPa） was established. It was shown that, the breakdown is occurred owing to the ionization wave, which starts from the electrode with small radius of curvature at both polarity of high voltage pulses. It is seen that formation of bright spots on the fiat electrode at the negative polarity of the electrode with small radius of curvature are observed during the changing of the discharge current polarity. It was shown that, at positive polarity of electrode with a small radius of curvature, the bright spots on the flat electrode arise due to the participation of the dynamic displacement current in the gap conductance.
文摘A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.
