Angular distribution of photoelectrons is investigated during the inner photoemissive effect for two variants: quantum of light basically reveals wave and basically corpuscular properties interacting with orbital elec...Angular distribution of photoelectrons is investigated during the inner photoemissive effect for two variants: quantum of light basically reveals wave and basically corpuscular properties interacting with orbital electron. Distinction in angular distribution of photoelectrons for these variants is demonstrated. Angular distribution in the second variant is investigated for the nonrelativistic and relativistic cases.展开更多
The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energ...The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energy sources. It is obvious that the interaction among solar light, semiconducting minerals, photoelectron/photohole, organics, inorganics, valence electrons and microorganisms occurs continuously on our planet. In a recent study, Lu et al. (2012) presented evidence demonstrating solar energy mediated by semiconducting mineral photocatalysis, acting as energy source, promoted the growth of some non-photosynthetic bacteria and revealed that the ternary system of microorganisms, minerals and solar light has played a critical role in the history of life on our planet. In simulated system, under simulated solar light semiconducting minerals, such as metal oxides and metal sulfides, generates photoelectrons which could be used by non-phototrophic microorganisms to support their metabolisms. The growth of microorganism was closely related to photon quantity and energy, and the microorganism growth and mineral light absorption spectra were fitted well under different light wavelengths. The overall energy efficiency from photon to biomass was 0.13‰ to 1.9‰. Further studies revealed that in natural soil systems, semiconducting mineral photocatalysis could influence the microbial population. Solar energy utilization pathway by nonphototrophic microorganisms mediated by semiconducting mineral photocatalysis provides a new concept to evaluate the origin and evolution of life. Semiconducting minerals are ubiquitous on Earth’s surface and widely participate in redox reactions following photoelectron-photohole pairs excited by solar light. As photoholes can be easily scavenged by environmental reductive substances and microorganisms possess multiple strategies to utilize extracellular electrons, the highly reductive photoelectrons serve as potential energy source for microbial life. The discovery of this pathway extends our knowledge on the use of solar energy by nonphototrophic microorganisms, and provides important clues to evaluate life on the early Earth. Microorganisms, minerals and solar light constitute a complex but important ternary system through Earth history. The discovery of the novel energy conversion pathway in this system demonstrates how nonphototrophic microorganisms directly or indirectly utilized photoelectrons as the solar energy source. The fully comprehending of nonphototrophic bacteria solar energy utilization conducted by semiconducting minerals in present environment will greatly help us to better understand the energy transform mechanism among interfaces of lithosphere, pedosphere, hydrosphere and biosphere.展开更多
Electron pitch angle distributions similar to bidirectional electron conics(BECs)have been reported at Mars in previous studies based on analyses of Mars Global Surveyor measurements.BEC distribution,also termed“butt...Electron pitch angle distributions similar to bidirectional electron conics(BECs)have been reported at Mars in previous studies based on analyses of Mars Global Surveyor measurements.BEC distribution,also termed“butterfly”distribution,presents a local minimum flux at 90°and a maximum flux before reaching the local loss cone.Previous studies have focused on 115 eV electrons that were produced mainly via solar wind electron impact ionization.Here using Solar Wind Electron Analyzer measurements made onboard the Mars Atmosphere and Volatile Evolution spacecraft,we identify 513 BEC events for 19-55 eV photoelectrons that were generated via photoionization only.Therefore,we are investigating electrons observed in regions well away from their source regions,to be distinguished from 115 eV electrons observed and produced in the same regions.We investigate the spatial distribution of the 19-55 eV BECs,revealing that they are more likely observed on the nightside as well as near strong crustal magnetic anomalies.We propose that the 19-55 eV photoelectron BECs are formed due to day-to-night transport and the magnetic mirror effect of photoelectrons moving along cross-terminator closed magnetic field lines.展开更多
The ZnO and Zn1-xMnxO minicrystal were synthesized by chemical vapor transport (CVT). The electron trap structure (donor level) and process on the temporal behavior of photoelectrons of materials were respectively stu...The ZnO and Zn1-xMnxO minicrystal were synthesized by chemical vapor transport (CVT). The electron trap structure (donor level) and process on the temporal behavior of photoelectrons of materials were respectively studied by thermo-luminescence and microwave absorption dielectric spectrometry. There are two peaks in the thermo-luminescence spectra in pure ZnO, one is -183 ℃ and the other is -127 ℃, which shows two kinds of electron trap energy level produced by the intrinsic defects in ZnO;but obtain very low thermo-luminescence that only equals to ten percent of pure ZnO in Zn1-xMnxO, which shows that its intensity of electron trap is less. The studies of microwave absorption dielectric spectrometry show that conduction band photoelectrons are two-step exponential decay process in ZnO, the lifetime of rapid process is 83 ns, while slow process is 828 ns, the reason of delay is relaxation effects of electron trap to conduction band photoelectrons. The intensity of electron trap is less in Zn1-xMnxO minicrystal, the relaxation effects of conduction band photoelectrons from electron trap is little, so electrons disappeared quickly at conduction band, and the decay process of photoelectrons is only 10～20 ns.展开更多
Non-resonant multiphoton ionization of atomic lead at 1064nm laser field has been studied.Both the angular distribution and the intensity dependence of photoelectrons have been measured.The results show that they are ...Non-resonant multiphoton ionization of atomic lead at 1064nm laser field has been studied.Both the angular distribution and the intensity dependence of photoelectrons have been measured.The results show that they are very sensitive to the process of multiphoton ionization.展开更多
The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from 1.6×10^(13) to 5.7×10^(13)W/cm^(2).Channel switching under di...The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from 1.6×10^(13) to 5.7×10^(13)W/cm^(2).Channel switching under different laser intensities is observed and identified in the photoelectron kinetic energy spectra of ammonia.Based on the photoelectron kinetic energy distributions and the photoelectron angular distributions,the characteristic peaks observed are exclusively assigned to the multiphoton resonance through certain intermediate states,followed by multiphoton above-threshold ionization.展开更多
Energy is the key issue of all life activities.The energy source and energy yielding pathway are the key scientific issues of the origin and early evolution of life on Earth.Current researches indicate that the utiliz...Energy is the key issue of all life activities.The energy source and energy yielding pathway are the key scientific issues of the origin and early evolution of life on Earth.Current researches indicate that the utilization of solar energy in large scale by life was an important breaking point of the early evolution of life on Earth and afterwards life gradually developed and flourished.However,in the widespread biochemical electron transfer of life activities,it is still not clear whether the electron source is sun or how electrons originated from sun.For billions of years,the ubiquitous semiconducting minerals in epigeosphere absorb solar energy,forming photoelectrons and photoholes.In reductive and weak acidic environment of early Earth,when photoholes were easily scavenged by reducing matters,photoelectrons were separated.Photoelectrons could effectively reduce carbon dioxide to organic matters,possibly providing organic matter foundation for the origin of life.Photoelectrons participated in photoelectron transfer chains driven by potential difference and transfer into primitive cells to maintain metabolisms.Semiconducting minerals,by absorbing ultraviolet,also protected primitive cells from being damaged by ultraviolet in the origin of life.Due to the continuous photoelectrons generation in semiconducting minerals and utilization by primitive cells,photoelectrons from semiconducting minerals’photocatalysis played multiple roles in the origin of life on early Earth,such as organic synthesis,cell protection,and energy supply.This mechanism still plays important roles in modern Earth surface systems.展开更多
Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ra...Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.展开更多
Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematicall...Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematically investigated using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray photoelectron spectroscopy(XPS),combined with Tafel polarization and electrochemical impedance spectroscopy(EIS)analyses.The findings showed that the alloying element Er refined the grain structure during solidification by increasing the nucleation rate and forming a secondary phase of Al_(3)Er with Al.The Er and Mg in the matrix co-oxidize to form a dense MgO/Er_(2)O_(3)composite oxide,preventing the formation of loose magnesium hydroxide/basic magnesium carbonate.The trace alloying element Mn interacts with impurities Fe in the magnesium matrix to form an AlFeMn second phase,reducing micro-galvanic corrosion driving force.Electrochemical testing in a 3.5%NaCl solution demonstrated a marked reduction in corrosion rate from 10.46 mm/a(AZ 31 Mn alloy)to 0.44 mm/a(AZ31Mn-1.2Er alloy).This research offers a reference for searching for corrosion-resistant magnesium alloy and degradable medical magnesium alloy materials.展开更多
The corrosion behaviors of an as-cast FeCoNiAl_(0.75)Cr_(1.25)high-entropy alloy(HEA)in acidic Na_(2)SO_(4)solution with different pH values were investigated.The results indicate that the as-cast FeCoNiAl_(0.75)Cr_(1...The corrosion behaviors of an as-cast FeCoNiAl_(0.75)Cr_(1.25)high-entropy alloy(HEA)in acidic Na_(2)SO_(4)solution with different pH values were investigated.The results indicate that the as-cast FeCoNiAl_(0.75)Cr_(1.25)HEA is mainly composed of face-centered cubic phase,body-centered cubic(BCC1)phase(Co–Cr–Fe)and ordered BCC(B2)phase(Ni–Al),in which BCC1 phase and B2 phase have a eutectic microstructure.Moreover,the corrosion of B2 phase occurs preferentially in a 0.05 mol/L SO_(4)^(2−)acidic solution.The electrochemical measurement results show that the corrosion resistance of the investigated HEA significantly changes as the solution pH increases from 2 to 2.5.This indicates that there is a critical pH in the range of 2–2.5 that affects the corrosion of HEA.In addition,the results of X-ray photoelectron spectroscopy prove that the surface film of FeCoNiAl_(0.75)Cr_(1.25)in SO_(4)^(2−)solution is formed with Al_(2)O_(3)and Cr_(2)O_(3)as the main components,and The content of Al2O3 and Cr_(2)O_(3)increases with increasing solution pH.展开更多
The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic pol...The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic polarization measurement,and electrochemical impedance spectroscopy.The results showed that the microstructure of this HEA displayed a dendritic morphology along with inter-dendritic regions.At the applied potential of–0.3,0,and 0.1 V vs.saturated calomel electrode(SCE),no significant damage to the surface of the alloy was observed.At the applied potentials of 0.15 and 0.2 V vs.SCE,selective detachment and tearing of the microstructure on the alloy surface were observed,attributed to micro-galvanic corrosion.HEA demonstrates typical spontaneous passivation behavior and exhibits capacitance at all five applied potentials.The energy dispersive spectroscopy results indicate significant elemental segregation within HEA,with a decrease in the content of Cr_(2)O_(3)in the passive film as the applied potential increases.Consequently,the protective efficacy of the passive film over the substrate in 0.5 mol/L NaOH solution was compromised.展开更多
Magnesium(Mg)alloys have attracted considerable attention as promising implant materials for biodegradable medical devices.In this study,we focused on investigating the effect of macroscopic environmental heterogeneit...Magnesium(Mg)alloys have attracted considerable attention as promising implant materials for biodegradable medical devices.In this study,we focused on investigating the effect of macroscopic environmental heterogeneity due to the degradation of Mg on its corrosion behavior.The immersion experiments using pure Mg plates,which were placed vertically in a culture medium(Dulbecco’s Modified Eagle’s Medium(DEME)+10%fetal bovine serum(FBS))for 1,5,and 10 days,were conducted.Surface analyses for the corrosion product layers and the measurements of the pH values and concentrations of eluted ions in the immersion medium around the upper and lower areas of the Mg plate were performed.The significant effect of the macroscopic environmental heterogeneity derived from Mg degradation on the corrosion behavior was demonstrated by in vitro tests.Additionally,the in vivo tests were carried out by implanting the pure Mg plates in the femur of rabbits.The in vivo results exhibited macroscopically heterogeneous Mg degradation,with areas of more severe corrosion compared to the in vitro test;it is especially noticeable during the early stage of degradation,even though the average corrosion rate was lower.展开更多
Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalizat...Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalization within a picosecond,forming a quasi-equilibrium distribution with overheated electrons.The high-energy tail of this distribution enables carriers to overcome energy barriers,thereby enhancing quantum efficiency—a phenomenon known as photothermionic emission(PTE).Despite its importance,the onset and mechanisms of PTE remain under debate.Using real-time timedependent density functional theory(rt-TDDFT),we investigate ultrafast carrier thermalization in two-dimensional(2D)materials graphene and PtTe2,and the results reveal distinct differences.In graphene,both electrons and holes thermalize into Fermi–Dirac distributions with good agreement to experiment,while PtTe2exhibits anomalous high-energy tails for both electrons and holes,deviating significantly from Fermi–Dirac behavior.We attribute this anomaly to differences in orbital coupling between the two materials,from which we derive design principles for identifying optimal PTE candidates and,ultimately,improving photodetector performance.展开更多
We have performed a comparative study of the photoelectron spectra adopting different initial states(2s or 2_(p0))of hydrogen atoms in a near-infrared laser pulse by using the full three-dimensional time-dependent Sch...We have performed a comparative study of the photoelectron spectra adopting different initial states(2s or 2_(p0))of hydrogen atoms in a near-infrared laser pulse by using the full three-dimensional time-dependent Schr?dinger equation.It is demonstrated that the atomic photoelectron spectra oscillate out of step as a function of electron kinetic energies for different initial states(2s or 2_(p0)),which is well reproduced by the simulations based on strong field approximation,and the above distinct feature is ascribed to the different interferences from the partial electron wave packets detached by positive and negative electric fields for different initial states of 2s and 2_(p0).展开更多
In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence ...In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence band offsets(VBO)of the three heterojunctions were measured by x-ray photoelectron spectroscopy(XPS),while the PtSe_(2)/n-GaN is 3.70±0.15 eV,PtSe_(2)/p-GaN is 0.264±0.15 eV,and PtSe_(2)/u-GaN is 3.02±0.15 eV.The conduction band offset(CBO)of the three heterojunctions was calculated from the material bandgap and VBO,while the PtSe_(2)/n-GaN is 0.61±0.15 eV,PtSe_(2)/p-GaN is 2.83±0.15 eV,and PtSe_(2)/u-GaN is 0.07±0.15 eV.This signifies that both PtSe_(2)/u-GaN and PtSe_(2)/p-GaN exhibit type-Ⅰband alignment,but the PtSe_(2)/n-GaN heterojunction has type-Ⅲband alignment.This signifies that the band engineering of PtSe_(2)/GaN heterojunction can be achieved by manipulating the concentration and type of doping,which is significantly relevant for the advancement of related devices through the realization of band alignment and the modulation of the material properties of the PtSe_(2)/GaN heterojunction.展开更多
A series of heteronuclear yttrium-nickel monoxide carbonyl complexes YNiO(CO)_(n)^(-)(n=1-5)were generated in a pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectrosco...A series of heteronuclear yttrium-nickel monoxide carbonyl complexes YNiO(CO)_(n)^(-)(n=1-5)were generated in a pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy combined with theoretical calculations.CO ligand-mediated reactivity in CO oxidation of yttrium-nickel monoxide carbonyl complexes was experimentally and theoretically identified.During the consecutive CO adsorption,aμ^(2)-O linear structure was most favorable for YNiO(CO)_(n)^(-)(n=1,2),then a structure in which the terminal O was bonded to the Y atom became favored for YNiO(CO)_(3)^(-),and finally a structure bearing a CO_(2)moiety was most favorable for YNiO(CO)_(n)^(-)(n=4,5).Theoretical calculations indicated that the Ni atom acted as an electron acceptor and accumulated electron density at n≤3,and then served as an electron donor along with the Y atom to contribute electron density in the rearrangement that accompanied CO oxidation at n>3.展开更多
We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state...We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state of 5s5p3P2 populated via the cascade transition 5s5p^(1)P_(1)→5s4d^(1)D_(2)→5s5p^(3)P_(2)accumulate a significant fraction,giving a long lifetime of 520 s.These atoms in the dark state are subsequently trapped by the gradient magnetic field of the MOT.By scanning the Sr+momentum distributions ionized with an 800 nm infrared femtosecond laser,we are able to outline the size of~0.55 mm in radius and the temperature of~0.40 mK for the dark-state atoms,which is significantly cooler than the MOT temperature of 3.3 mK trapped in the 461 nm.The size of MOT exhibits an oblate spheroidal distribution with a radius of approximately 0.35 mm and 0.55 mm,extracted with momenta of photoion and absorption imaging,respectively.The results using the photoion momenta are consistent with the expected results from absorption imaging,which confirms the method's reliability.The advantage of this method is the ability to simultaneously characterize the distribution information of atoms in different initial states within the cold atomic cloud.展开更多
The development of an analytical method for determining the properties of quantum dots(QDs)is crucial for improving the optical performance of QD-based displays.Therefore,synchrotron-based X-ray photoelectron spectros...The development of an analytical method for determining the properties of quantum dots(QDs)is crucial for improving the optical performance of QD-based displays.Therefore,synchrotron-based X-ray photoelectron spectroscopy(XPS)is designed here to accurately characterize the chemical and structural differences between different QDs.This method enables the determination of the reason for the minimal differences between the optical properties of different QDs depending on the synthesis process,which is difficult to determine using conventional methods alone.Combined with model simulations,the XPS spectra obtained at different photon energies reveal the internal structures and chemical-state distributions of the QDs.In particular,the QD synthesized under optimal conditions demonstrates a relatively lower degree of oxidation of the core and more uniformly stacked ZnSe/ZnS shell layers.The internal structures and chemical-state distributions of QDs are closely related to their optical properties.Finally,the synchrotron-based XPS proposed here can be applied to compare nearly equivalent QDs with slightly different optical properties.展开更多
Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been ...Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been reached through tight focusing of the light spot(nano-ARPES).At present,the lower limit of the spot size of the light on the sample has been reached.Another way to further improve the spatial resolution is through using apertures to only let electrons from a small area of the sample pass.With both back-focal plane and image apertures,the size of the selected area can be as small as 20 nm.Yet,without aberration correction,the maximum opening angle at the sample for 20 nm spatial resolution is usually smaller than 3°,making this method not suitable for nano-ARPES.As shown in this paper,a conventional aberration corrector,which corrects chromatic and third-order spherical aberrations,is not enough either.Only when the fifth-order spherical aberration is also corrected,the opening angle at the sample is large enough for nano-ARPES.In this paper,the design of a time-of-fight PEEM/ARPES/nano-ARPES instrument,which is currently under development at the Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,is presented.The main point of innovation is a fiveelectrode electron mirror corrector,which is used to correct simultaneously chromatic,third-order and fifth-order spherical aberrations,resulting in 1 nm spatial resolution with~230 mrad aperture angle in PEEM mode.This makes feasible the method of using apertures to improve the spatial resolution of the nano-ARPES mode.A new design of the magnetic prism array(MPA)is also presented,which preserves the rotational symmetry better than the existing designs.展开更多
The alignment-dependent photoelectron spectrum is a valuable tool for mapping out the electronic structure of molecular orbitals.However,this approach may not be applicable to all molecules,such as CO_(2),as the ioniz...The alignment-dependent photoelectron spectrum is a valuable tool for mapping out the electronic structure of molecular orbitals.However,this approach may not be applicable to all molecules,such as CO_(2),as the ionization process in a linearly polarized laser field involves contributions from orbitals other than the highest occupied molecular orbital(HOMO).Here,we conducted a theoretical investigation into the ionization process of N_(2) and CO_(2) in near-circularly polarized laser field using the Coulomb-corrected strong-field approximation(CCSFA)method for molecules.In particular,we introduced a generalized dressed state into the CCSFA method in order to account for the impact of the laser field on the molecular initial state.The simulated alignment-dependent photoelectron momentum distribution(PMD)of the two molecules exhibited markedly disparate behaviors,which were in excellent agreement with the previous experimental observations reported in[Phys.Rev.A 102,013117(2020)].Our findings indicate that under a near-circularly polarized laser field,the alignment-dependent PMD of molecules is primarily sourced from the HOMO,in contrast to the situation under a linearly polarized laser field.Moreover,a satisfactory correlation between the alignment-dependent angular distribution and the orbital symmetry was observed,which suggests an effective approach for molecular orbital imaging.展开更多
文摘Angular distribution of photoelectrons is investigated during the inner photoemissive effect for two variants: quantum of light basically reveals wave and basically corpuscular properties interacting with orbital electron. Distinction in angular distribution of photoelectrons for these variants is demonstrated. Angular distribution in the second variant is investigated for the nonrelativistic and relativistic cases.
文摘The Earth surface is a multiple open system. Semiconducting minerals, including most metal oxides and sulfides, absorb visible light of the solar spectrum. Microorganisms evolve varied pathways to get carbon and energy sources. It is obvious that the interaction among solar light, semiconducting minerals, photoelectron/photohole, organics, inorganics, valence electrons and microorganisms occurs continuously on our planet. In a recent study, Lu et al. (2012) presented evidence demonstrating solar energy mediated by semiconducting mineral photocatalysis, acting as energy source, promoted the growth of some non-photosynthetic bacteria and revealed that the ternary system of microorganisms, minerals and solar light has played a critical role in the history of life on our planet. In simulated system, under simulated solar light semiconducting minerals, such as metal oxides and metal sulfides, generates photoelectrons which could be used by non-phototrophic microorganisms to support their metabolisms. The growth of microorganism was closely related to photon quantity and energy, and the microorganism growth and mineral light absorption spectra were fitted well under different light wavelengths. The overall energy efficiency from photon to biomass was 0.13‰ to 1.9‰. Further studies revealed that in natural soil systems, semiconducting mineral photocatalysis could influence the microbial population. Solar energy utilization pathway by nonphototrophic microorganisms mediated by semiconducting mineral photocatalysis provides a new concept to evaluate the origin and evolution of life. Semiconducting minerals are ubiquitous on Earth’s surface and widely participate in redox reactions following photoelectron-photohole pairs excited by solar light. As photoholes can be easily scavenged by environmental reductive substances and microorganisms possess multiple strategies to utilize extracellular electrons, the highly reductive photoelectrons serve as potential energy source for microbial life. The discovery of this pathway extends our knowledge on the use of solar energy by nonphototrophic microorganisms, and provides important clues to evaluate life on the early Earth. Microorganisms, minerals and solar light constitute a complex but important ternary system through Earth history. The discovery of the novel energy conversion pathway in this system demonstrates how nonphototrophic microorganisms directly or indirectly utilized photoelectrons as the solar energy source. The fully comprehending of nonphototrophic bacteria solar energy utilization conducted by semiconducting minerals in present environment will greatly help us to better understand the energy transform mechanism among interfaces of lithosphere, pedosphere, hydrosphere and biosphere.
基金supported by the B-type Strategic Priority Program No.XDB4100000funded by the Chinese Academy of Sciences and the pre-research projects on Civil Aerospace Technologies No.D020105 and D020104+1 种基金funded by China’s National Space Administrationthe National Natural Science Foundation of China through grants 41525015,41774186,and 41904154.
文摘Electron pitch angle distributions similar to bidirectional electron conics(BECs)have been reported at Mars in previous studies based on analyses of Mars Global Surveyor measurements.BEC distribution,also termed“butterfly”distribution,presents a local minimum flux at 90°and a maximum flux before reaching the local loss cone.Previous studies have focused on 115 eV electrons that were produced mainly via solar wind electron impact ionization.Here using Solar Wind Electron Analyzer measurements made onboard the Mars Atmosphere and Volatile Evolution spacecraft,we identify 513 BEC events for 19-55 eV photoelectrons that were generated via photoionization only.Therefore,we are investigating electrons observed in regions well away from their source regions,to be distinguished from 115 eV electrons observed and produced in the same regions.We investigate the spatial distribution of the 19-55 eV BECs,revealing that they are more likely observed on the nightside as well as near strong crustal magnetic anomalies.We propose that the 19-55 eV photoelectron BECs are formed due to day-to-night transport and the magnetic mirror effect of photoelectrons moving along cross-terminator closed magnetic field lines.
基金Project supported by the National Natural Science Foundation of China (50472037) the Natural Science Foundation of Hebei Province (E2004000117 and F2004000130) the Science and Technology Research Program from the Bureau of Science and Technology of Hebei Province (2002158)
文摘The ZnO and Zn1-xMnxO minicrystal were synthesized by chemical vapor transport (CVT). The electron trap structure (donor level) and process on the temporal behavior of photoelectrons of materials were respectively studied by thermo-luminescence and microwave absorption dielectric spectrometry. There are two peaks in the thermo-luminescence spectra in pure ZnO, one is -183 ℃ and the other is -127 ℃, which shows two kinds of electron trap energy level produced by the intrinsic defects in ZnO;but obtain very low thermo-luminescence that only equals to ten percent of pure ZnO in Zn1-xMnxO, which shows that its intensity of electron trap is less. The studies of microwave absorption dielectric spectrometry show that conduction band photoelectrons are two-step exponential decay process in ZnO, the lifetime of rapid process is 83 ns, while slow process is 828 ns, the reason of delay is relaxation effects of electron trap to conduction band photoelectrons. The intensity of electron trap is less in Zn1-xMnxO minicrystal, the relaxation effects of conduction band photoelectrons from electron trap is little, so electrons disappeared quickly at conduction band, and the decay process of photoelectrons is only 10～20 ns.
文摘Non-resonant multiphoton ionization of atomic lead at 1064nm laser field has been studied.Both the angular distribution and the intensity dependence of photoelectrons have been measured.The results show that they are very sensitive to the process of multiphoton ionization.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574116,11534004,11704147,and 10704028)。
文摘The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from 1.6×10^(13) to 5.7×10^(13)W/cm^(2).Channel switching under different laser intensities is observed and identified in the photoelectron kinetic energy spectra of ammonia.Based on the photoelectron kinetic energy distributions and the photoelectron angular distributions,the characteristic peaks observed are exclusively assigned to the multiphoton resonance through certain intermediate states,followed by multiphoton above-threshold ionization.
基金supported by National Natural Science Foundation of China(Grant No.41230103)National Basic Research Program of China(Grant No.2014CB846001)
文摘Energy is the key issue of all life activities.The energy source and energy yielding pathway are the key scientific issues of the origin and early evolution of life on Earth.Current researches indicate that the utilization of solar energy in large scale by life was an important breaking point of the early evolution of life on Earth and afterwards life gradually developed and flourished.However,in the widespread biochemical electron transfer of life activities,it is still not clear whether the electron source is sun or how electrons originated from sun.For billions of years,the ubiquitous semiconducting minerals in epigeosphere absorb solar energy,forming photoelectrons and photoholes.In reductive and weak acidic environment of early Earth,when photoholes were easily scavenged by reducing matters,photoelectrons were separated.Photoelectrons could effectively reduce carbon dioxide to organic matters,possibly providing organic matter foundation for the origin of life.Photoelectrons participated in photoelectron transfer chains driven by potential difference and transfer into primitive cells to maintain metabolisms.Semiconducting minerals,by absorbing ultraviolet,also protected primitive cells from being damaged by ultraviolet in the origin of life.Due to the continuous photoelectrons generation in semiconducting minerals and utilization by primitive cells,photoelectrons from semiconducting minerals’photocatalysis played multiple roles in the origin of life on early Earth,such as organic synthesis,cell protection,and energy supply.This mechanism still plays important roles in modern Earth surface systems.
基金supported by the Vinnova(project number 2020-03778)supported by the Swedish Research Council(Vetenskapsradet,project number 2021-04157).
文摘Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.
基金Projects(82171030,81870678)supported by the National Natural Science Foundation of China。
文摘Magnesium alloys as medical implant materials necessitate a lower and adjustable corrosion rate for clinical applications.The microstructure and corrosion behavior of AZ31Mn-xEr(x=0.1,0.5,1.2)alloys were systematically investigated using optical microscopy(OM),scanning electron microscopy(SEM),and X-ray photoelectron spectroscopy(XPS),combined with Tafel polarization and electrochemical impedance spectroscopy(EIS)analyses.The findings showed that the alloying element Er refined the grain structure during solidification by increasing the nucleation rate and forming a secondary phase of Al_(3)Er with Al.The Er and Mg in the matrix co-oxidize to form a dense MgO/Er_(2)O_(3)composite oxide,preventing the formation of loose magnesium hydroxide/basic magnesium carbonate.The trace alloying element Mn interacts with impurities Fe in the magnesium matrix to form an AlFeMn second phase,reducing micro-galvanic corrosion driving force.Electrochemical testing in a 3.5%NaCl solution demonstrated a marked reduction in corrosion rate from 10.46 mm/a(AZ 31 Mn alloy)to 0.44 mm/a(AZ31Mn-1.2Er alloy).This research offers a reference for searching for corrosion-resistant magnesium alloy and degradable medical magnesium alloy materials.
基金supported by Key Laboratory of Research on Hydraulic and Hydro-Power Equipment Surface Engineering Technology of Zhejiang Province(20240304).
文摘The corrosion behaviors of an as-cast FeCoNiAl_(0.75)Cr_(1.25)high-entropy alloy(HEA)in acidic Na_(2)SO_(4)solution with different pH values were investigated.The results indicate that the as-cast FeCoNiAl_(0.75)Cr_(1.25)HEA is mainly composed of face-centered cubic phase,body-centered cubic(BCC1)phase(Co–Cr–Fe)and ordered BCC(B2)phase(Ni–Al),in which BCC1 phase and B2 phase have a eutectic microstructure.Moreover,the corrosion of B2 phase occurs preferentially in a 0.05 mol/L SO_(4)^(2−)acidic solution.The electrochemical measurement results show that the corrosion resistance of the investigated HEA significantly changes as the solution pH increases from 2 to 2.5.This indicates that there is a critical pH in the range of 2–2.5 that affects the corrosion of HEA.In addition,the results of X-ray photoelectron spectroscopy prove that the surface film of FeCoNiAl_(0.75)Cr_(1.25)in SO_(4)^(2−)solution is formed with Al_(2)O_(3)and Cr_(2)O_(3)as the main components,and The content of Al2O3 and Cr_(2)O_(3)increases with increasing solution pH.
基金funded by National Key Research and Development Program of China(No.2021YFB3401100)Evaluation Project of Guangdong Provincial Key Laboratory(No.2023B1212060043)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)GDAS'Project of Science and Technology Development(Nos.2023GDASQNRC-0205 and 2024GDASZH-2024010102).
文摘The corrosion behavior of CoCrCu_(0.1)FeMoNi high entropy alloy(HEA)in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,potentiodynamic polarization measurement,and electrochemical impedance spectroscopy.The results showed that the microstructure of this HEA displayed a dendritic morphology along with inter-dendritic regions.At the applied potential of–0.3,0,and 0.1 V vs.saturated calomel electrode(SCE),no significant damage to the surface of the alloy was observed.At the applied potentials of 0.15 and 0.2 V vs.SCE,selective detachment and tearing of the microstructure on the alloy surface were observed,attributed to micro-galvanic corrosion.HEA demonstrates typical spontaneous passivation behavior and exhibits capacitance at all five applied potentials.The energy dispersive spectroscopy results indicate significant elemental segregation within HEA,with a decrease in the content of Cr_(2)O_(3)in the passive film as the applied potential increases.Consequently,the protective efficacy of the passive film over the substrate in 0.5 mol/L NaOH solution was compromised.
基金supported by JSPS KAKENHI Grant Number 22K12903.
文摘Magnesium(Mg)alloys have attracted considerable attention as promising implant materials for biodegradable medical devices.In this study,we focused on investigating the effect of macroscopic environmental heterogeneity due to the degradation of Mg on its corrosion behavior.The immersion experiments using pure Mg plates,which were placed vertically in a culture medium(Dulbecco’s Modified Eagle’s Medium(DEME)+10%fetal bovine serum(FBS))for 1,5,and 10 days,were conducted.Surface analyses for the corrosion product layers and the measurements of the pH values and concentrations of eluted ions in the immersion medium around the upper and lower areas of the Mg plate were performed.The significant effect of the macroscopic environmental heterogeneity derived from Mg degradation on the corrosion behavior was demonstrated by in vitro tests.Additionally,the in vivo tests were carried out by implanting the pure Mg plates in the femur of rabbits.The in vivo results exhibited macroscopically heterogeneous Mg degradation,with areas of more severe corrosion compared to the in vitro test;it is especially noticeable during the early stage of degradation,even though the average corrosion rate was lower.
基金Project supported by the Natural Science Foundation of Chongqing of China(Grant No.CSTB2023NSCQ-LZX0087)the National Natural Science Foundation of China(Grant Nos.62074021 and 12174380)。
文摘Understanding the dynamics of photoexcited carriers is essential for advancing photoelectronic device design.Photon absorption generates electron–hole pairs,and subsequent scatterings can induce ultrafast thermalization within a picosecond,forming a quasi-equilibrium distribution with overheated electrons.The high-energy tail of this distribution enables carriers to overcome energy barriers,thereby enhancing quantum efficiency—a phenomenon known as photothermionic emission(PTE).Despite its importance,the onset and mechanisms of PTE remain under debate.Using real-time timedependent density functional theory(rt-TDDFT),we investigate ultrafast carrier thermalization in two-dimensional(2D)materials graphene and PtTe2,and the results reveal distinct differences.In graphene,both electrons and holes thermalize into Fermi–Dirac distributions with good agreement to experiment,while PtTe2exhibits anomalous high-energy tails for both electrons and holes,deviating significantly from Fermi–Dirac behavior.We attribute this anomaly to differences in orbital coupling between the two materials,from which we derive design principles for identifying optimal PTE candidates and,ultimately,improving photodetector performance.
基金Project supported by Li Ka Shing Foundation STUGTIIT Joint Research(Grant No.2024LKSFG02)the STU Scientific Research Foundation for Talents(Grant Nos.NTF22026,NTF23011,NTF23014,and NTF23036T)+1 种基金the National Basic Research Program of China(Grant No.2019YFA0307700)the National Natural Science Foundation of China(Grant Nos.12074239 and 12274300)。
文摘We have performed a comparative study of the photoelectron spectra adopting different initial states(2s or 2_(p0))of hydrogen atoms in a near-infrared laser pulse by using the full three-dimensional time-dependent Schr?dinger equation.It is demonstrated that the atomic photoelectron spectra oscillate out of step as a function of electron kinetic energies for different initial states(2s or 2_(p0)),which is well reproduced by the simulations based on strong field approximation,and the above distinct feature is ascribed to the different interferences from the partial electron wave packets detached by positive and negative electric fields for different initial states of 2s and 2_(p0).
基金Project supported by the National Natural Science Foundation of China(Grant No.61874108)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-04)the Gansu Provincial Scientific and Technologic Planning Program(Grant No.22ZD6GE016).
文摘In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence band offsets(VBO)of the three heterojunctions were measured by x-ray photoelectron spectroscopy(XPS),while the PtSe_(2)/n-GaN is 3.70±0.15 eV,PtSe_(2)/p-GaN is 0.264±0.15 eV,and PtSe_(2)/u-GaN is 3.02±0.15 eV.The conduction band offset(CBO)of the three heterojunctions was calculated from the material bandgap and VBO,while the PtSe_(2)/n-GaN is 0.61±0.15 eV,PtSe_(2)/p-GaN is 2.83±0.15 eV,and PtSe_(2)/u-GaN is 0.07±0.15 eV.This signifies that both PtSe_(2)/u-GaN and PtSe_(2)/p-GaN exhibit type-Ⅰband alignment,but the PtSe_(2)/n-GaN heterojunction has type-Ⅲband alignment.This signifies that the band engineering of PtSe_(2)/GaN heterojunction can be achieved by manipulating the concentration and type of doping,which is significantly relevant for the advancement of related devices through the realization of band alignment and the modulation of the material properties of the PtSe_(2)/GaN heterojunction.
基金supported by the Natural Science Foundation of Shandong Province(No.ZR2021QB215)the National Natural Science Foundation of China(Nos.22273101,22125303,92061203,21327901,and 22288201)+2 种基金Dalian Institute of Chemical Physics(No.DICP I202437)the Talent Induction Program for Youth Innovation Teams in Colleges and Universities of Shandong Province(No.2022-2024)the Talent Introduction Research Start-up Funds of Ludong University(No.20212026)。
文摘A series of heteronuclear yttrium-nickel monoxide carbonyl complexes YNiO(CO)_(n)^(-)(n=1-5)were generated in a pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy combined with theoretical calculations.CO ligand-mediated reactivity in CO oxidation of yttrium-nickel monoxide carbonyl complexes was experimentally and theoretically identified.During the consecutive CO adsorption,aμ^(2)-O linear structure was most favorable for YNiO(CO)_(n)^(-)(n=1,2),then a structure in which the terminal O was bonded to the Y atom became favored for YNiO(CO)_(3)^(-),and finally a structure bearing a CO_(2)moiety was most favorable for YNiO(CO)_(n)^(-)(n=4,5).Theoretical calculations indicated that the Ni atom acted as an electron acceptor and accumulated electron density at n≤3,and then served as an electron donor along with the Y atom to contribute electron density in the rearrangement that accompanied CO oxidation at n>3.
基金Project supported by the Natural Science Foundation of Henan(Grant No.252300421304)the National Natural Science Foundation of China(Grant Nos.12204498,12474259+1 种基金12334011)the National Key Research and Development Program of China(Grant No.2022YFA1604302)。
文摘We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state of 5s5p3P2 populated via the cascade transition 5s5p^(1)P_(1)→5s4d^(1)D_(2)→5s5p^(3)P_(2)accumulate a significant fraction,giving a long lifetime of 520 s.These atoms in the dark state are subsequently trapped by the gradient magnetic field of the MOT.By scanning the Sr+momentum distributions ionized with an 800 nm infrared femtosecond laser,we are able to outline the size of~0.55 mm in radius and the temperature of~0.40 mK for the dark-state atoms,which is significantly cooler than the MOT temperature of 3.3 mK trapped in the 461 nm.The size of MOT exhibits an oblate spheroidal distribution with a radius of approximately 0.35 mm and 0.55 mm,extracted with momenta of photoion and absorption imaging,respectively.The results using the photoion momenta are consistent with the expected results from absorption imaging,which confirms the method's reliability.The advantage of this method is the ability to simultaneously characterize the distribution information of atoms in different initial states within the cold atomic cloud.
基金Advanced Light Source,which is a DOE Office of Science User Facility under contract no.DE-AC02-05CH11231the Basque Government for funding through a PhD Fellowship(Grant no.PRE_2018_2_0285)+1 种基金through Egonlabur Travel Fellowship(Grant no.EP_2018_1_0004)partially supported by an Early Career Award in the Condensed Phase and Interfacial Molecular Science Program,in the Chemical Sciences Geosciences and Biosciences Division of the Office of Basic Energy Sciences of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231.
文摘The development of an analytical method for determining the properties of quantum dots(QDs)is crucial for improving the optical performance of QD-based displays.Therefore,synchrotron-based X-ray photoelectron spectroscopy(XPS)is designed here to accurately characterize the chemical and structural differences between different QDs.This method enables the determination of the reason for the minimal differences between the optical properties of different QDs depending on the synthesis process,which is difficult to determine using conventional methods alone.Combined with model simulations,the XPS spectra obtained at different photon energies reveal the internal structures and chemical-state distributions of the QDs.In particular,the QD synthesized under optimal conditions demonstrates a relatively lower degree of oxidation of the core and more uniformly stacked ZnSe/ZnS shell layers.The internal structures and chemical-state distributions of QDs are closely related to their optical properties.Finally,the synchrotron-based XPS proposed here can be applied to compare nearly equivalent QDs with slightly different optical properties.
基金supported by Shanghai Tech University and Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,China(Grant No.SZZX2301006)。
文摘Over the past few decades,angle-resolved photoemission spectroscopy(ARPES)has been one of the important tools to study electronic structure of crystals.In recent years,the spatial resolution of around 150 nm has been reached through tight focusing of the light spot(nano-ARPES).At present,the lower limit of the spot size of the light on the sample has been reached.Another way to further improve the spatial resolution is through using apertures to only let electrons from a small area of the sample pass.With both back-focal plane and image apertures,the size of the selected area can be as small as 20 nm.Yet,without aberration correction,the maximum opening angle at the sample for 20 nm spatial resolution is usually smaller than 3°,making this method not suitable for nano-ARPES.As shown in this paper,a conventional aberration corrector,which corrects chromatic and third-order spherical aberrations,is not enough either.Only when the fifth-order spherical aberration is also corrected,the opening angle at the sample is large enough for nano-ARPES.In this paper,the design of a time-of-fight PEEM/ARPES/nano-ARPES instrument,which is currently under development at the Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area,is presented.The main point of innovation is a fiveelectrode electron mirror corrector,which is used to correct simultaneously chromatic,third-order and fifth-order spherical aberrations,resulting in 1 nm spatial resolution with~230 mrad aperture angle in PEEM mode.This makes feasible the method of using apertures to improve the spatial resolution of the nano-ARPES mode.A new design of the magnetic prism array(MPA)is also presented,which preserves the rotational symmetry better than the existing designs.
基金supported by the National Natural Science Foundation of China(Grant No.12274273).
文摘The alignment-dependent photoelectron spectrum is a valuable tool for mapping out the electronic structure of molecular orbitals.However,this approach may not be applicable to all molecules,such as CO_(2),as the ionization process in a linearly polarized laser field involves contributions from orbitals other than the highest occupied molecular orbital(HOMO).Here,we conducted a theoretical investigation into the ionization process of N_(2) and CO_(2) in near-circularly polarized laser field using the Coulomb-corrected strong-field approximation(CCSFA)method for molecules.In particular,we introduced a generalized dressed state into the CCSFA method in order to account for the impact of the laser field on the molecular initial state.The simulated alignment-dependent photoelectron momentum distribution(PMD)of the two molecules exhibited markedly disparate behaviors,which were in excellent agreement with the previous experimental observations reported in[Phys.Rev.A 102,013117(2020)].Our findings indicate that under a near-circularly polarized laser field,the alignment-dependent PMD of molecules is primarily sourced from the HOMO,in contrast to the situation under a linearly polarized laser field.Moreover,a satisfactory correlation between the alignment-dependent angular distribution and the orbital symmetry was observed,which suggests an effective approach for molecular orbital imaging.
