Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presente...Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron tem- perature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method.展开更多
The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical...The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in coherent state are calculated. It is found that the spectrum structure is influenced significantly by the cavity damping constant k, and the spectrum structure is dependent on the interaction time r when the cavity dissipation is present. Only one peak located at wa appears in the atomic spectra for larger T.展开更多
We theoretically investigate the emission spectrum for a A-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak po...We theoretically investigate the emission spectrum for a A-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum.展开更多
We theoretically analyze the steady state emission spectrum and transient temporal dynamics in a coupled biexciton quantum dot（QD）–cavity system. For steady state, a phonon-assisted biexciton–exciton cascade model...We theoretically analyze the steady state emission spectrum and transient temporal dynamics in a coupled biexciton quantum dot（QD）–cavity system. For steady state, a phonon-assisted biexciton–exciton cascade model under continuous wave（CW） excitation is presented to explain the asymmetric QD–cavity emission spectrum intensities（intensities of cavity,exciton, and biexciton emission peak） in off-resonance condition. Results demonstrate that the electron–phonon process is crucial to the asymmetry of emission spectrum intensity. Moreover the transient characteristics of the biexciton–exciton cascade system under pulse excitation show abundant nonlinear temporal dynamic behaviors, including complicated oscillations which are caused by the four-level structure of QD model. We also reveal that under off-resonance condition the cavity outputs are slightly reduced due to the electron–phonon interaction.展开更多
An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a te...An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.展开更多
We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to cal...We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal. Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency. It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels. For a zero initial phase, destructive property is presented in the spectra. With the increase of initial phase difference, quantum interference between the two decay channels from upper levels to ground level turns to be constructive. Furthermore, we give an interpretation for the property of these spectra.展开更多
The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These...The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http：//www.astrnomy.csdb.cn/EIE/.展开更多
This paper studies the interaction of a A-type three-level atom with a single mode field. It discusses the emission spectrum characteristics of the A-type three-level atom driven by the photon-added coherent field. By...This paper studies the interaction of a A-type three-level atom with a single mode field. It discusses the emission spectrum characteristics of the A-type three-level atom driven by the photon-added coherent field. By means of the second-order degree of coherence, it shows some nonclassical properties of the cavity field, such as sub-Poissonian photon- number distribution and the two-time intensity-intensity correlation which violates the Cauchy Schwarz inequality.展开更多
A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(...A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.展开更多
A large-gap uniform discharge is ignited by a coaxial dielectric barrier discharge and burns between a needle anode and a plate cathode under a low sustaining voltage by feeding with flowing argon. The basic aspects o...A large-gap uniform discharge is ignited by a coaxial dielectric barrier discharge and burns between a needle anode and a plate cathode under a low sustaining voltage by feeding with flowing argon. The basic aspects of the large-gap uniform discharge are investigated by optical and spectroscopic methods. From the discharge images, it can be found that this discharge has similar regions with glow discharge at low pressure except a plasma plume region. Light emission signals from the discharge indicate that the plasma column is invariant with time, while there are some stochastic pulses in the plasma plume region. The optical emission spectra scanning from 300 nm to 800 nm are used to calculate the excited electron temperature and vibrational temperature of the large-gap uniform discharge. It has been found that the excited electron temperature almost keeps constant and the vibrational temperature increases with increasing discharge current. Both of them decreases with increasing gas flow rate.展开更多
Dielectric barrier discharge （DBD） between two cylindrical glass containers with salt water generated by a nanosecond repetitively pulsed power generator is reported. The electrical parameters, luminous images and s...Dielectric barrier discharge （DBD） between two cylindrical glass containers with salt water generated by a nanosecond repetitively pulsed power generator is reported. The electrical parameters, luminous images and spectrum diagnosis are presented. It is shown that the DBD possesses a large discharge current and an intense optical emission from the nitrogen second positive system below 400 nm. The gas temperature remains very close to room temperature regardless of pulse polarity. Luminous photographs with a short exposure time down to 2 ns indicate that no filament is observed and the discharge is homogeneous.展开更多
The electric and plasma characteristics of RF discharge plasma actuation under varying pressure have been inves- tigated experimentally. As the pressure increases, the shapes of charge-voltage Lissajous curves vary, a...The electric and plasma characteristics of RF discharge plasma actuation under varying pressure have been inves- tigated experimentally. As the pressure increases, the shapes of charge-voltage Lissajous curves vary, and the discharge energy increases. The emission spectra show significant difference as the pressure varies. When the pressure is 1000 Pa, the electron temperature is estimated to be 4.139 eV, the electron density and the vibrational temperature of plasma are /peak /lPeak which describes the electron temper- 4.71 x 10^11 cm-3 and 1.27 eV, respectively. The ratio of spectral lines ＂391.4/＇380.5 ature hardly changes when the pressure varies between 5000-30000 Pa, while it increases remarkably with the pressure below 5000 Pa, indicating a transition from filamentary discharge to glow discharge. The characteristics of emission spec- trum are obviously influenced by the loading power. With more loading power, both of the illumination and emission spectrum intensity increase at 10000 Pa. The pin-pin electrode RF discharge is arc-like at power higher than 33 W, which results in a macroscopic air temperature increase.展开更多
By adopting the optical multi-channel analyzer combined with fourier transform infrared （FTIR） spectrometer, the dominant free radicals and products generated by arc discharge were measured and studied, and the main...By adopting the optical multi-channel analyzer combined with fourier transform infrared （FTIR） spectrometer, the dominant free radicals and products generated by arc discharge were measured and studied, and the main plasma chemical reaction process in the nitric oxide production by arc discharge was identified. Plasma chemical kinetic curves of O, O2, N2, N and NO were simulated by using CHEMKIN and MATLAB. The results show that the main plasma chemical reaction process of nitric oxide production by arc discharge is a replacement reaction between O and N2, where NO can be generated instantaneously when discharging reaches stable.展开更多
In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharg...In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.展开更多
Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites.In order to understand the physical mechanism...Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites.In order to understand the physical mechanism of APPTs,high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes.The plume images and spectra at different times and positions are experimentally recorded,and the spatial distribution,composition,and trajectory of plasmas can be concluded through analyzing them.With the increase of the distance from the ablation surface,two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.展开更多
Non-thermal plasma at atmospheric pressure was explored for the preparation of polysilicon from SiCl4. The power supply sources of positive pulse and alternating current （8 kHz and 100 kHz） were compared for polysil...Non-thermal plasma at atmospheric pressure was explored for the preparation of polysilicon from SiCl4. The power supply sources of positive pulse and alternating current （8 kHz and 100 kHz） were compared for polysilicon preparation. The samples prepared by using the 100 kHz power source were crystalline silicon. The effects of H2 and SiCl4 volume fractions were investigated. The optical emission spectra showed that silicon species played an important role in polysilicon deposition展开更多
The spontaneous emission decay dynamics of a tripod configuration four-level atom driven by a single laser field is studied. Under different initial conditions, we discuss the effects of quantum interference and detun...The spontaneous emission decay dynamics of a tripod configuration four-level atom driven by a single laser field is studied. Under different initial conditions, we discuss the effects of quantum interference and detuning of external driving field on atomic spontaneous emission properties. For the larger detuning, the interesting phenomena of the spectral line narrowing are found which stem from the contribution of external driving field.展开更多
In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of ...In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of （CH3）eCO, CH3NO2, CHzBr2, and CHBr3 at ~ 213 nm. The CH product intensity is measured by using the emission spectrum of CH （A2△→XeH）. The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH （Ae△） product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.展开更多
In this paper,high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration.Temporal-spatia...In this paper,high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration.Temporal-spatial distributions of discharge images,the emission intensities of optical emission spectra,and plasma vibrational and rotational temperatures are investigated.By analyzing the evolution of vibrational and rotational temperatures in space and time dimensions,the energy distribution and energy transfer process in plasma are also discussed.It is found that a diffuse structure with high density plasma concentrated in the region near the needle tip can be presented in nanosecond pulsed discharge,and an obvious energy transfer from electronic energy to vibration energy can be observed in each discharge pulse.展开更多
A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied vo...A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given.展开更多
基金supported by National Natural Science Foundation of China(Nos.10675121,10705028 and 10605025)National Basic Research Program of China(No.2008CB717800)
文摘Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron tem- perature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10574060)
文摘The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in coherent state are calculated. It is found that the spectrum structure is influenced significantly by the cavity damping constant k, and the spectrum structure is dependent on the interaction time r when the cavity dissipation is present. Only one peak located at wa appears in the atomic spectra for larger T.
文摘We theoretically investigate the emission spectrum for a A-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61275201 and 61372037)the Beijing Municipal Excellent Ph.D. Thesis Guidance Foundation(Grant No.20131001301)the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),China
文摘We theoretically analyze the steady state emission spectrum and transient temporal dynamics in a coupled biexciton quantum dot（QD）–cavity system. For steady state, a phonon-assisted biexciton–exciton cascade model under continuous wave（CW） excitation is presented to explain the asymmetric QD–cavity emission spectrum intensities（intensities of cavity,exciton, and biexciton emission peak） in off-resonance condition. Results demonstrate that the electron–phonon process is crucial to the asymmetry of emission spectrum intensity. Moreover the transient characteristics of the biexciton–exciton cascade system under pulse excitation show abundant nonlinear temporal dynamic behaviors, including complicated oscillations which are caused by the four-level structure of QD model. We also reveal that under off-resonance condition the cavity outputs are slightly reduced due to the electron–phonon interaction.
文摘An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10904025 and 10674037)the National Basic Research and Development Program of China(Grant No.2007CB307001)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20092302120024)the Program for Excellent Team in Harbin Institute of Technology
文摘We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal. Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency. It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels. For a zero initial phase, destructive property is presented in the spectra. With the increase of initial phase difference, quantum interference between the two decay channels from upper levels to ground level turns to be constructive. Furthermore, we give an interpretation for the property of these spectra.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10204024, 10373014, 10433010 and 10474138）.
文摘The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http：//www.astrnomy.csdb.cn/EIE/.
基金supported by the National Natural Science Foundation of China (Grants Nos 10674052 and 60878004)
文摘This paper studies the interaction of a A-type three-level atom with a single mode field. It discusses the emission spectrum characteristics of the A-type three-level atom driven by the photon-added coherent field. By means of the second-order degree of coherence, it shows some nonclassical properties of the cavity field, such as sub-Poissonian photon- number distribution and the two-time intensity-intensity correlation which violates the Cauchy Schwarz inequality.
基金supported by National Natural Science Foundation of China(Nos.12375250,11875121,51977057 and 11805013)the Natural Science Foundation of Hebei Province(Nos.A2020201025 and A2022201036)+3 种基金Hebei Province Optoelectronic Information Materials Laboratory Performance Subsidy Fund Project(No.22567634H)Funds for Distinguished Young Scientists of Hebei Province(No.A2012201045)the Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908 and DXK202011)the Post-graduate’s Innovation Fund Project of Hebei University(No.HBU2022bs004)。
文摘A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.
基金supported by the National Natural Science Foundation of China(Grant Nos.10805013 and 51077035)the Funds for Distinguished Young Scientists of Hebei Province of China(Grant No.A2012201045)+4 种基金the Natural Science Foundation of Hebei Province of China(Grant No.A2011201132)the Department of Education for Outstanding Youth Project of China(Grant No.Y2011120)the Funds for Distinguished Young Scientists of Hebei University of China(Grant No.2010J02)the Doctor Program of Hebei University of China(Grant No.2012-241)the Youth Project of Hebei University of China(GrantNo.2011Q14)
文摘A large-gap uniform discharge is ignited by a coaxial dielectric barrier discharge and burns between a needle anode and a plate cathode under a low sustaining voltage by feeding with flowing argon. The basic aspects of the large-gap uniform discharge are investigated by optical and spectroscopic methods. From the discharge images, it can be found that this discharge has similar regions with glow discharge at low pressure except a plasma plume region. Light emission signals from the discharge indicate that the plasma column is invariant with time, while there are some stochastic pulses in the plasma plume region. The optical emission spectra scanning from 300 nm to 800 nm are used to calculate the excited electron temperature and vibrational temperature of the large-gap uniform discharge. It has been found that the excited electron temperature almost keeps constant and the vibrational temperature increases with increasing discharge current. Both of them decreases with increasing gas flow rate.
基金supported by National Natural Science Foundation of China (Nos. 50707032, 11076026)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KGCX2-YW-339)+1 种基金the National Basic Research Program of China (No. 2011CB209405)the State Key Laboratory of Control and Simulation of Power Systems and Generating Equipment in Tsinghua University (No. SKLD09KZ05)
文摘Dielectric barrier discharge （DBD） between two cylindrical glass containers with salt water generated by a nanosecond repetitively pulsed power generator is reported. The electrical parameters, luminous images and spectrum diagnosis are presented. It is shown that the DBD possesses a large discharge current and an intense optical emission from the nitrogen second positive system below 400 nm. The gas temperature remains very close to room temperature regardless of pulse polarity. Luminous photographs with a short exposure time down to 2 ns indicate that no filament is observed and the discharge is homogeneous.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11472306,51336011,and 51407197)
文摘The electric and plasma characteristics of RF discharge plasma actuation under varying pressure have been inves- tigated experimentally. As the pressure increases, the shapes of charge-voltage Lissajous curves vary, and the discharge energy increases. The emission spectra show significant difference as the pressure varies. When the pressure is 1000 Pa, the electron temperature is estimated to be 4.139 eV, the electron density and the vibrational temperature of plasma are /peak /lPeak which describes the electron temper- 4.71 x 10^11 cm-3 and 1.27 eV, respectively. The ratio of spectral lines ＂391.4/＇380.5 ature hardly changes when the pressure varies between 5000-30000 Pa, while it increases remarkably with the pressure below 5000 Pa, indicating a transition from filamentary discharge to glow discharge. The characteristics of emission spec- trum are obviously influenced by the loading power. With more loading power, both of the illumination and emission spectrum intensity increase at 10000 Pa. The pin-pin electrode RF discharge is arc-like at power higher than 33 W, which results in a macroscopic air temperature increase.
基金supported by National Natural Science Foundation of China(No.50677026)Postgraduates Innovation Foundation of Huazhong University of Science and Technology of China(HF-08-11-2011-261)the third batch of Teaching Research Foundation of "Teaching Quality Project" in Huazhong University of Science and Technology of China(No.46)
文摘By adopting the optical multi-channel analyzer combined with fourier transform infrared （FTIR） spectrometer, the dominant free radicals and products generated by arc discharge were measured and studied, and the main plasma chemical reaction process in the nitric oxide production by arc discharge was identified. Plasma chemical kinetic curves of O, O2, N2, N and NO were simulated by using CHEMKIN and MATLAB. The results show that the main plasma chemical reaction process of nitric oxide production by arc discharge is a replacement reaction between O and N2, where NO can be generated instantaneously when discharging reaches stable.
基金The project supported by the United Fund of the National Natural Science Foundation of China and the Engineering Physics Institute of China (No. 10276008)the funding of Liaoning Province Natural Science Foundation (No. 20022138)
文摘In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3sαS0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.
基金National Natural Science Foundation of China(No.11772354)for the financial assistance provided for this work。
文摘Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites.In order to understand the physical mechanism of APPTs,high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes.The plume images and spectra at different times and positions are experimentally recorded,and the spatial distribution,composition,and trajectory of plasmas can be concluded through analyzing them.With the increase of the distance from the ablation surface,two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.
基金support from the Scientific Research Fund of Liaoning Provincial Education Department for Colleges and Universities of China (No. 2008T229)
文摘Non-thermal plasma at atmospheric pressure was explored for the preparation of polysilicon from SiCl4. The power supply sources of positive pulse and alternating current （8 kHz and 100 kHz） were compared for polysilicon preparation. The samples prepared by using the 100 kHz power source were crystalline silicon. The effects of H2 and SiCl4 volume fractions were investigated. The optical emission spectra showed that silicon species played an important role in polysilicon deposition
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10904025,10674037 and 50836002)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20092302120024)+3 种基金the China Postdoctoral Science Foundation (Grant No. 20090451007)the Development Program for Outstanding Young Teachers in Harbin Institute of Technology,China (Grant No. HITQNJS. 2009. 030.)the National Basic Research Program of China (Grant No. 2007CB307001)the Program of Excellent Team in Harbin Institute of Technology China
文摘The spontaneous emission decay dynamics of a tripod configuration four-level atom driven by a single laser field is studied. Under different initial conditions, we discuss the effects of quantum interference and detuning of external driving field on atomic spontaneous emission properties. For the larger detuning, the interesting phenomena of the spectral line narrowing are found which stem from the contribution of external driving field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10674047,10804031,10904037,10904060,10974055,11034002,11274114,and 61205198)the National Key Basic Research and Development Program of China(Grant Nos.2006CB921604 and 2011CB921602)+2 种基金the Basic Key Program of Shanghai Municipality,China(Grant No.07JC14017)the Fundamental Research Funds for the Central Universitiesthe Shanghai Leading Academic Discipline Project,China(Grant No.B408)
文摘In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of （CH3）eCO, CH3NO2, CHzBr2, and CHBr3 at ~ 213 nm. The CH product intensity is measured by using the emission spectrum of CH （A2△→XeH）. The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH （Ae△） product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.
基金supported by the Key Project of Chinese National Programs for Research and Development(No. 2016YFC0207200)National Natural Science Foundation of China(Nos.51677019,51407022,51377014)
文摘In this paper,high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration.Temporal-spatial distributions of discharge images,the emission intensities of optical emission spectra,and plasma vibrational and rotational temperatures are investigated.By analyzing the evolution of vibrational and rotational temperatures in space and time dimensions,the energy distribution and energy transfer process in plasma are also discussed.It is found that a diffuse structure with high density plasma concentrated in the region near the needle tip can be presented in nanosecond pulsed discharge,and an obvious energy transfer from electronic energy to vibration energy can be observed in each discharge pulse.
基金supported by the National Natural Science Foundation of China(Nos.10375015,10575027)supported in part by the Natural Science Foundation of Hebei University
文摘A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given.
