Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented.Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO_(2) laser pulses.Teflon is a C-based...Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented.Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO_(2) laser pulses.Teflon is a C-based polymer that is,among other things,interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples.This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes.Evaluation of plasma parameters was done using several spectroscopic techniques.Stark profiles of appropriate C ionic lines were used to determine electron number density.The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature.A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder,peripheral parts of plasma.We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements.展开更多
Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architect...Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.展开更多
In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and ac...In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.展开更多
Eu Mossbauer spectra of BaFBr:Eu phosphor are reported for the first time.The results show that f(Eu(2+) )<f(Eu(3+)) or <x2>Eu(2+)><x2>Eu(3+),which indicates that the attraction between phonons and E...Eu Mossbauer spectra of BaFBr:Eu phosphor are reported for the first time.The results show that f(Eu(2+) )<f(Eu(3+)) or <x2>Eu(2+)><x2>Eu(3+),which indicates that the attraction between phonons and Eu(2+) is stronger than that between phonons and Eu(3+),this may cause a faster increase of f(Eu=(2+)vs f(Eu(3+)) when temperature decreases as observed in the experiments.It is also found from Mossbauer investigation that when temperature decreases,the relative content of Eu(2+) decreases, while that of Eu(3+) increases.The temperature dependent Mossbauer spectra provide evidence for electron exchange or hopping between Eu(2+) or Eu(3+) sites in BaFBr lattice. The Mossbauer results are discussed and compared with the results of XPS and Photoluminescence studies.展开更多
Y2O2S:Sm^3+, Mg^2+, Ti^4+ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a...Y2O2S:Sm^3+, Mg^2+, Ti^4+ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 + molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 + (4G5/2→6HJ ,J = 5/2, 7/2, 9/2), and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 + molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4+ phosphor prepared by co-precipitation method was Sm^3+ ions. The results indicated that the Y2O2S : Sm^3+ , Mg^2+ , an efficient long afterglow phosphor.展开更多
In this paper,nitrogen dielectric barrier discharge(DBD) plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow(FN) in the range of 0-1...In this paper,nitrogen dielectric barrier discharge(DBD) plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow(FN) in the range of 0-1 m3/h,the plasma optical emission spectra(OES) were measured and studied.The vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen were obtained,by fitting the rovibronic bands of N_2(C^3∏_u-B^3∏_g,0-1),and by the Boltzmann plot method for purposes of comparison.T_(vib) increased up to 2481 K with increasing nitrogen flow till0.2 m3/h,and then decreased with further increasing FN,while Trot decreased monotonously and approached to-350 K for FN ≥ 0.6 m^3/h.The intensity of N_2(C^3∏_u-B^3∏_g,0-0,1-0,0-3) and N_2~+(B^2∑_u~+-X^2Σ_g~+,0-0) exhibited similar evolution with increasing FN to those of the T_(vib) and Trot,respectively.The discharge photos revealed that the discharge filaments gradually decreased with increasing FN,and eventually disappeared,which implied that a discharge mode transition emerged with increasing FN.The possible mechanism for the discharge mode transition is studied in detail according to the vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen.展开更多
The P-branch emission spectra of (4,1) and (3,1) bands of the A^1П-X^1∑^+ system of IrN molecule are studied using an analytical formula which is derived from elementary expression of molecular total energy by...The P-branch emission spectra of (4,1) and (3,1) bands of the A^1П-X^1∑^+ system of IrN molecule are studied using an analytical formula which is derived from elementary expression of molecular total energy by taking multiple spectral differences. It not only reproduces the known experimental transition lines, but also predicts the unknown spectral lines up to J = 80 for each band by using a group of fifteen known experimental transition lines.展开更多
Nano-Y_2O_3:Eu^(3+) powder was prepared by the homogeneous precipitation. With controlling the conditions of the reaction, nano powders with different grain size were obtained. It is found that the blue-shift phenomen...Nano-Y_2O_3:Eu^(3+) powder was prepared by the homogeneous precipitation. With controlling the conditions of the reaction, nano powders with different grain size were obtained. It is found that the blue-shift phenomena exist in the nano-Y2O3:Eu3+ emission spectra excited by X-ray. The wave lengths of the peak (5D0→7F2) are related with the grain size of the powder展开更多
Er^3+ :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 + ions in th...Er^3+ :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 + ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.展开更多
In this paper,volume coupled surface barrier discharge(V-SBD) with three structures possessing different volumes is excited by sine AC power in atmospheric air.Discharge images,waveforms of applied voltage and disch...In this paper,volume coupled surface barrier discharge(V-SBD) with three structures possessing different volumes is excited by sine AC power in atmospheric air.Discharge images,waveforms of applied voltage and discharge current,and optical emission spectra simulating rotational and vibrational temperatures are recorded and analyzed.The effects of applied voltage on emission intensities of N2(C^3Πu→ B^3Πg) and N2^+(B^2∑u^+ → X^2Eg^+),and rotational and vibrational temperatures are investigated.The results show that as applied voltage rises,emission intensities and rotational temperatures increase while vibrational temperatures decrease.In addition it is found that,as applied voltage varies,the rotational temperature of surface discharge changes faster than that of volume discharge.展开更多
In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier dischar...In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier discharge (V-SBD) excited by bipolar nanosecond high-voltage pulse power in atmospheric air. The excited V-SBDs consist of surface barrier discharge (d = 0 mm) and volume added surface barrier discharges (d = 2 mm and 3 mm). The optical emission spectra are recorded for calculating emission intensities of N2 (C3 ∏u → B3∏g) and N2+ (B2 ∑u+ → X2 ∑g+), and simulating rotational and vibrational temperatures. The influences of gap distance of V-SBD on emission intensity and plasma temperature are also investigated and analyzed. The results show that d = 0 mm structure can excite the largest emission intensity of N2 (C3 ∏u → B3 ∏g), while the existence of volume barrier discharge can delay the occurrence of the peak value of the emission intensity ratio of N2 + (B2 ∑u+ → X2 ∑+g)/N2 (C3 ∏u → B3 ∏g) during the rising period of the applied voltage pulse and weaken it during the end period. The increasing factor of emission intensity is effected by the pulse repetition rate. The d = 3 mm structure has the highest threshold voltage while it can maintain more emission intensity of N2 (C3 ∏u→ B3∏g) than that of d = 2 mm structure. The structure of d = 2 mm can maintain more increasing factor than that of the d = 3 mm structure with varying pulse repetition rate. Besides, the rotational temperatures of three V-SBD structures are slightly affected when the gap distance and pulse repetition rate vary. The vibrational temperatures have decaying tendencies of all three structures with the increasing pulse repetition rate.展开更多
The spontaneous emission property ofΛ-type three-level atom driven by the bichromatic field in the anisotropic double-band photonic crystal is calculated by n-times iteration method.The influence of different paramet...The spontaneous emission property ofΛ-type three-level atom driven by the bichromatic field in the anisotropic double-band photonic crystal is calculated by n-times iteration method.The influence of different parameters on atomic spontaneous emission is studied,and the phenomena of atomic spontaneous emission are explained in the dressed state representation.It is found that the spontaneous emission spectra of the atom driven by the bichromatic field presents a multi-peak comb structure.The position of the emission peak is determined by the initial state of the atom,and the interval between the neighboring emission peaks is the detuningδof the bichromatic field.When the ratio between Rabi frequency intensity and the detuningδof the bichromatic field remains unchanged,the intensity of each emitted peak remains invariant.The spontaneously emitted peak can be annihilated in the band gap and enhanced near the band edge in the anisotropic photonic crystals.Meanwhile,we also observe the fluorescence quenching phenomenon in the spontaneous emission spectra.The research in this paper provides the theoretical guidance for the control of atomic spontaneous emission.展开更多
In this work,a floating electrode is employed to generate a stable large-area diffuse discharge plasma under an open oxygen-rich environment.The discharge image and the optical emission spectra of the N2(C-B),N2+(B-X)...In this work,a floating electrode is employed to generate a stable large-area diffuse discharge plasma under an open oxygen-rich environment.The discharge image and the optical emission spectra of the N2(C-B),N2+(B-X),N2(B-A),and O(3p–3s,777 nm)are measured to analyze the morphological and optical characteristics of the discharge.The effects of applied voltage,gas flow rate,and electrode gap on the reactive species,vibrational temperature and rotational temperature are investigated,and the discharge mode is discussed by simulating the electrostatic field before the breakdown.It is found that the changes of applied voltage and electrode gap causes the transition of the discharge modes among corona mode,diffuse discharge mode and spark mode.It is shown that the floating electrode can inhibit the transition from discharge to spark mode to a certain extent,which is conducive to maintaining the stability of discharge.As is vividly illustrated in this study,the increase of applied voltage or the decrease of electrode gap contributes to the generation of more active particles,such as N2(C)andN+2(B).Furthermore,the Joule heating effect becomes more evident with the increased applied voltage when the electrode gap is 15 and 20 mm.Moreover,as the applied voltage increases,the vibrational temperature increases at the electrode gap of 25 mm.展开更多
The accurate analysis of the elemental composition plays a crucial role in the research of functional materials.The emitting characteristic x-ray fluorescence(XRF)photons can be used for precisely discriminating the s...The accurate analysis of the elemental composition plays a crucial role in the research of functional materials.The emitting characteristic x-ray fluorescence(XRF)photons can be used for precisely discriminating the specified element.The detection accuracy of conventional XRF methodology using semiconductor detector is limited by the energy resolution,thus posing a challenge in accurately scaling the actual energy of each XRF photon.We adopt a novel high-resolution x-ray spectrometer based on the superconducting transition-edge sensor(TES)for the XRF spectroscopy measurement of different elements.Properties including high energy resolution,high detection efficiency and precise linearity of the new spectrometer will bring significant benefits in analyzing elemental composition via XRF.In this paper,we study the Ledge emission line profiles of three adjacent rare earth elements with the evenly mixed sample of their oxide components:terbium,dysprosium and holmium.Two orders of magnitude better energy resolution are obtained compared to a commercial silicon drift detector.With this TES-based spectrometer,the spectral lines overlapped or interfered by background can be clearly distinguished,thus making the chemical component analysis more accurate and quantitative.A database of coefficient values for the line strength of the spectrum can then be constructed thereafter.Equipped with the novel XRF spectrometer and an established coefficient database,a direct analysis of the composition proportion of a certain element in an unknown sample can be achieved with high accuracy.展开更多
Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the ...Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.展开更多
Nanosized ZnS doped with different concentrations of Eu3+ were prepared andanalyzed by x-ray diffraction technique. The experimental results show that ZnS belongs to thecubic structure. From the photoluminescence (PL)...Nanosized ZnS doped with different concentrations of Eu3+ were prepared andanalyzed by x-ray diffraction technique. The experimental results show that ZnS belongs to thecubic structure. From the photoluminescence (PL) emission spectra, it can be seen that the ratioof the emission intensity of Eu3+ at 616 nm to that at 590 nm increases as the increasing of Eu3+.This phenomenon reveals that the site symmetry of Eu3+ reduces as the increasing of Eu3+.展开更多
In this paper we report on an experimental study of the characteristics of nanosecond pulsed discharge plasma aerodynamic actuation. The N2 (C3IIu) rotational and vibrational temperatures are around 430 K and 0.24 e...In this paper we report on an experimental study of the characteristics of nanosecond pulsed discharge plasma aerodynamic actuation. The N2 (C3IIu) rotational and vibrational temperatures are around 430 K and 0.24 eV, respectively. The emission intensity ratio between tile first negative system and the second positive system of N2, as a rough indicator of the temporally and spatially averaged electron energy, has a minor dependence on applied voltage amplitude. The induced flow direction is not parallel, but vertical to the dielectric layer surface, as shown by measurements of body force, velocity, and vorticity. Nanosecond discharge plasma aerodynamic actuation is effective in airfoil flow separation control at freestream speeds up to 100 m/s.展开更多
To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio (PO2/PTiCl4 〉 1). However, this may lead to the formation of powder instead of fil...To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio (PO2/PTiCl4 〉 1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 (PO2/PTiC14 = 2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.展开更多
Dielectric barrier discharge (DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide (CuO). Power X-ray diffraction (XRD) was used to characterize ...Dielectric barrier discharge (DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide (CuO). Power X-ray diffraction (XRD) was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra (OES) were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen (H) radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.展开更多
Non-thermal C/H/Ar plasmas are widely applied to carbonaceous material production and processing.In this work,plasma parameters and gaseous species of the atmospheric non-thermal C/H/Ar plasmas produced by an atmosphe...Non-thermal C/H/Ar plasmas are widely applied to carbonaceous material production and processing.In this work,plasma parameters and gaseous species of the atmospheric non-thermal C/H/Ar plasmas produced by an atmospheric-pressure DC arc discharge generator in CH_4/Ar were investigated.The voltage-current characteristics were measured for different CH_4/Ar ratios.Optical emission spectroscopy was employed to analyze the electron excitation temperature,gas temperature and electron density under various discharge conditions.The hydrocarbon molecules produced in the CH4/Ar plasmas were detected with photoionization mass spectrometry.The optical spectral results demonstrated that the electron excitation temperature was 0.4-1 eV,the gas temperature was 2800-4200 K and the electron density was in the range of(5-20)×10^15 cm^-3.The mass spectrum indicated that a variety of unsaturated hydrocarbons(C2H4,C3H6,C6H6,etc.) and several highly unsaturated hydrocarbons(C4H2,C5H6,etc.) were produced in the non-thermal arc plasmas.展开更多
基金funded by the Ministry of Education,Science and Technological Development of the Republic of Serbia(Nos.451-03-68/2022-14/200017 and 451-03-68/2022-14/200146)the financial support of the State Committee on Science and Technology of the Republic of Belarusthe Belarusian Republican Foundation for Fundamental Research(No.F20SRBG-001)。
文摘Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented.Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO_(2) laser pulses.Teflon is a C-based polymer that is,among other things,interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples.This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes.Evaluation of plasma parameters was done using several spectroscopic techniques.Stark profiles of appropriate C ionic lines were used to determine electron number density.The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature.A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder,peripheral parts of plasma.We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements.
文摘Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.
基金supported by National Natural Science Foundations of China(Nos.51977023 and 52077026)the Fundamental Research Funds for the Central Universities(No.DUT23YG227)。
文摘In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.
文摘Eu Mossbauer spectra of BaFBr:Eu phosphor are reported for the first time.The results show that f(Eu(2+) )<f(Eu(3+)) or <x2>Eu(2+)><x2>Eu(3+),which indicates that the attraction between phonons and Eu(2+) is stronger than that between phonons and Eu(3+),this may cause a faster increase of f(Eu=(2+)vs f(Eu(3+)) when temperature decreases as observed in the experiments.It is also found from Mossbauer investigation that when temperature decreases,the relative content of Eu(2+) decreases, while that of Eu(3+) increases.The temperature dependent Mossbauer spectra provide evidence for electron exchange or hopping between Eu(2+) or Eu(3+) sites in BaFBr lattice. The Mossbauer results are discussed and compared with the results of XPS and Photoluminescence studies.
基金Project supported by the Hebei Developing Foundation of Science&Technology (51215103b)
文摘Y2O2S:Sm^3+, Mg^2+, Ti^4+ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 + molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 + (4G5/2→6HJ ,J = 5/2, 7/2, 9/2), and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 + molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4+ phosphor prepared by co-precipitation method was Sm^3+ ions. The results indicated that the Y2O2S : Sm^3+ , Mg^2+ , an efficient long afterglow phosphor.
基金supported by National Natural Science Foundation of China(Nos.11475040,11375041)the Fundamental Research Funds for the Central Universities(No.DUT14ZD[G]04)
文摘In this paper,nitrogen dielectric barrier discharge(DBD) plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow(FN) in the range of 0-1 m3/h,the plasma optical emission spectra(OES) were measured and studied.The vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen were obtained,by fitting the rovibronic bands of N_2(C^3∏_u-B^3∏_g,0-1),and by the Boltzmann plot method for purposes of comparison.T_(vib) increased up to 2481 K with increasing nitrogen flow till0.2 m3/h,and then decreased with further increasing FN,while Trot decreased monotonously and approached to-350 K for FN ≥ 0.6 m^3/h.The intensity of N_2(C^3∏_u-B^3∏_g,0-0,1-0,0-3) and N_2~+(B^2∑_u~+-X^2Σ_g~+,0-0) exhibited similar evolution with increasing FN to those of the T_(vib) and Trot,respectively.The discharge photos revealed that the discharge filaments gradually decreased with increasing FN,and eventually disappeared,which implied that a discharge mode transition emerged with increasing FN.The possible mechanism for the discharge mode transition is studied in detail according to the vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen.
基金supported by the National Natural Science Foundation of China (Grant No.11074204)the Science Foundation of the Ministry of Education of China (Grant No.20100181110085)+1 种基金the Research Fund of Key Disciplines of Atomic and Molecular Physicsthe Fund of Key Laboratory of Advanced Scientific Computation,Xihua University,China
文摘The P-branch emission spectra of (4,1) and (3,1) bands of the A^1П-X^1∑^+ system of IrN molecule are studied using an analytical formula which is derived from elementary expression of molecular total energy by taking multiple spectral differences. It not only reproduces the known experimental transition lines, but also predicts the unknown spectral lines up to J = 80 for each band by using a group of fifteen known experimental transition lines.
文摘Nano-Y_2O_3:Eu^(3+) powder was prepared by the homogeneous precipitation. With controlling the conditions of the reaction, nano powders with different grain size were obtained. It is found that the blue-shift phenomena exist in the nano-Y2O3:Eu3+ emission spectra excited by X-ray. The wave lengths of the peak (5D0→7F2) are related with the grain size of the powder
文摘Er^3+ :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 + ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.
基金supported by National Natural Science Foundation of China(Grant Nos.51377014,51407022 and 51677019)the National Key Research and Development program of China(No.2016YFC0207200)
文摘In this paper,volume coupled surface barrier discharge(V-SBD) with three structures possessing different volumes is excited by sine AC power in atmospheric air.Discharge images,waveforms of applied voltage and discharge current,and optical emission spectra simulating rotational and vibrational temperatures are recorded and analyzed.The effects of applied voltage on emission intensities of N2(C^3Πu→ B^3Πg) and N2^+(B^2∑u^+ → X^2Eg^+),and rotational and vibrational temperatures are investigated.The results show that as applied voltage rises,emission intensities and rotational temperatures increase while vibrational temperatures decrease.In addition it is found that,as applied voltage varies,the rotational temperature of surface discharge changes faster than that of volume discharge.
基金supported by National Key R&D Program of China (2016YFC0207200)National Natural Science Foundation of China (Nos. 51377014, 51407022 and 51677019)
文摘In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier discharge (V-SBD) excited by bipolar nanosecond high-voltage pulse power in atmospheric air. The excited V-SBDs consist of surface barrier discharge (d = 0 mm) and volume added surface barrier discharges (d = 2 mm and 3 mm). The optical emission spectra are recorded for calculating emission intensities of N2 (C3 ∏u → B3∏g) and N2+ (B2 ∑u+ → X2 ∑g+), and simulating rotational and vibrational temperatures. The influences of gap distance of V-SBD on emission intensity and plasma temperature are also investigated and analyzed. The results show that d = 0 mm structure can excite the largest emission intensity of N2 (C3 ∏u → B3 ∏g), while the existence of volume barrier discharge can delay the occurrence of the peak value of the emission intensity ratio of N2 + (B2 ∑u+ → X2 ∑+g)/N2 (C3 ∏u → B3 ∏g) during the rising period of the applied voltage pulse and weaken it during the end period. The increasing factor of emission intensity is effected by the pulse repetition rate. The d = 3 mm structure has the highest threshold voltage while it can maintain more emission intensity of N2 (C3 ∏u→ B3∏g) than that of d = 2 mm structure. The structure of d = 2 mm can maintain more increasing factor than that of the d = 3 mm structure with varying pulse repetition rate. Besides, the rotational temperatures of three V-SBD structures are slightly affected when the gap distance and pulse repetition rate vary. The vibrational temperatures have decaying tendencies of all three structures with the increasing pulse repetition rate.
基金Project supported by the Natural Science Foundation of Jilin Province of China(Grant No.20220101031JC)。
文摘The spontaneous emission property ofΛ-type three-level atom driven by the bichromatic field in the anisotropic double-band photonic crystal is calculated by n-times iteration method.The influence of different parameters on atomic spontaneous emission is studied,and the phenomena of atomic spontaneous emission are explained in the dressed state representation.It is found that the spontaneous emission spectra of the atom driven by the bichromatic field presents a multi-peak comb structure.The position of the emission peak is determined by the initial state of the atom,and the interval between the neighboring emission peaks is the detuningδof the bichromatic field.When the ratio between Rabi frequency intensity and the detuningδof the bichromatic field remains unchanged,the intensity of each emitted peak remains invariant.The spontaneously emitted peak can be annihilated in the band gap and enhanced near the band edge in the anisotropic photonic crystals.Meanwhile,we also observe the fluorescence quenching phenomenon in the spontaneous emission spectra.The research in this paper provides the theoretical guidance for the control of atomic spontaneous emission.
基金supported by National Natural Science Foundations of China(Nos.11965018,51977023 and 52077026)the Science and Technology Development Fund of Xinjiang Production and Construction of China(No.2019BC009)+2 种基金the Fundamental Research Funds for the Central Universities of China(No.DUT21LK31)the Key Laboratory Fund of National Defense Science and Technology of China(No.6142605200303)Science and Technology Plan Project of the Ninth Division of the Crops of China(No.2021JS003)。
文摘In this work,a floating electrode is employed to generate a stable large-area diffuse discharge plasma under an open oxygen-rich environment.The discharge image and the optical emission spectra of the N2(C-B),N2+(B-X),N2(B-A),and O(3p–3s,777 nm)are measured to analyze the morphological and optical characteristics of the discharge.The effects of applied voltage,gas flow rate,and electrode gap on the reactive species,vibrational temperature and rotational temperature are investigated,and the discharge mode is discussed by simulating the electrostatic field before the breakdown.It is found that the changes of applied voltage and electrode gap causes the transition of the discharge modes among corona mode,diffuse discharge mode and spark mode.It is shown that the floating electrode can inhibit the transition from discharge to spark mode to a certain extent,which is conducive to maintaining the stability of discharge.As is vividly illustrated in this study,the increase of applied voltage or the decrease of electrode gap contributes to the generation of more active particles,such as N2(C)andN+2(B).Furthermore,the Joule heating effect becomes more evident with the increased applied voltage when the electrode gap is 15 and 20 mm.Moreover,as the applied voltage increases,the vibrational temperature increases at the electrode gap of 25 mm.
基金the National Major Scientific Research Instrument Development Project(Grant No.11927805)the National Key Research and Development Program of China(Grant No.2022YFF0608303)+2 种基金the NSFC Young Scientists Fund(Grant No.12005134)the Shanghai-XFEL Beamline Project(SBP)(Grant No.31011505505885920161A2101001)the Shanghai Municipal Science and Technology Major Project(Grant No.2017SHZDZX02)。
文摘The accurate analysis of the elemental composition plays a crucial role in the research of functional materials.The emitting characteristic x-ray fluorescence(XRF)photons can be used for precisely discriminating the specified element.The detection accuracy of conventional XRF methodology using semiconductor detector is limited by the energy resolution,thus posing a challenge in accurately scaling the actual energy of each XRF photon.We adopt a novel high-resolution x-ray spectrometer based on the superconducting transition-edge sensor(TES)for the XRF spectroscopy measurement of different elements.Properties including high energy resolution,high detection efficiency and precise linearity of the new spectrometer will bring significant benefits in analyzing elemental composition via XRF.In this paper,we study the Ledge emission line profiles of three adjacent rare earth elements with the evenly mixed sample of their oxide components:terbium,dysprosium and holmium.Two orders of magnitude better energy resolution are obtained compared to a commercial silicon drift detector.With this TES-based spectrometer,the spectral lines overlapped or interfered by background can be clearly distinguished,thus making the chemical component analysis more accurate and quantitative.A database of coefficient values for the line strength of the spectrum can then be constructed thereafter.Equipped with the novel XRF spectrometer and an established coefficient database,a direct analysis of the composition proportion of a certain element in an unknown sample can be achieved with high accuracy.
基金supported by National Natural Science Foundation of China (No. 11975047)。
文摘Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.
文摘Nanosized ZnS doped with different concentrations of Eu3+ were prepared andanalyzed by x-ray diffraction technique. The experimental results show that ZnS belongs to thecubic structure. From the photoluminescence (PL) emission spectra, it can be seen that the ratioof the emission intensity of Eu3+ at 616 nm to that at 590 nm increases as the increasing of Eu3+.This phenomenon reveals that the site symmetry of Eu3+ reduces as the increasing of Eu3+.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50906100 and 10972236)the Science Foundation of National Excellent Doctoral Dissertation of China (Grant No. 201172)
文摘In this paper we report on an experimental study of the characteristics of nanosecond pulsed discharge plasma aerodynamic actuation. The N2 (C3IIu) rotational and vibrational temperatures are around 430 K and 0.24 eV, respectively. The emission intensity ratio between tile first negative system and the second positive system of N2, as a rough indicator of the temporally and spatially averaged electron energy, has a minor dependence on applied voltage amplitude. The induced flow direction is not parallel, but vertical to the dielectric layer surface, as shown by measurements of body force, velocity, and vorticity. Nanosecond discharge plasma aerodynamic actuation is effective in airfoil flow separation control at freestream speeds up to 100 m/s.
基金supported by National Natural Science Foundation of China(Nos.10835004,51077009)the Fundamental Research Funds for the Central Universities
文摘To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio (PO2/PTiCl4 〉 1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 (PO2/PTiC14 = 2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.
基金supported by National Natural Science Foundation of China(No.21173028)the Science and Technology Research Project of Liaoning Provincial Education Department of China(No.L2013464)the Scientific Research Foundation for the Doctor of Liaoning Province of China(No.20131004)
文摘Dielectric barrier discharge (DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide (CuO). Power X-ray diffraction (XRD) was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra (OES) were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen (H) radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.
基金supported by National Natural Science Foundation of China(Nos.11035005,11475174,50876101)USTC-NSRL Association Funding(No.KY2090130001)
文摘Non-thermal C/H/Ar plasmas are widely applied to carbonaceous material production and processing.In this work,plasma parameters and gaseous species of the atmospheric non-thermal C/H/Ar plasmas produced by an atmospheric-pressure DC arc discharge generator in CH_4/Ar were investigated.The voltage-current characteristics were measured for different CH_4/Ar ratios.Optical emission spectroscopy was employed to analyze the electron excitation temperature,gas temperature and electron density under various discharge conditions.The hydrocarbon molecules produced in the CH4/Ar plasmas were detected with photoionization mass spectrometry.The optical spectral results demonstrated that the electron excitation temperature was 0.4-1 eV,the gas temperature was 2800-4200 K and the electron density was in the range of(5-20)×10^15 cm^-3.The mass spectrum indicated that a variety of unsaturated hydrocarbons(C2H4,C3H6,C6H6,etc.) and several highly unsaturated hydrocarbons(C4H2,C5H6,etc.) were produced in the non-thermal arc plasmas.