Laser-induced fluorescence(LIF)spectroscopy is employed for plasma diagnosis,necessitating the utilization of deconvolution algorithms to isolate the Doppler effect from the raw spectral signal.However,direct deconvol...Laser-induced fluorescence(LIF)spectroscopy is employed for plasma diagnosis,necessitating the utilization of deconvolution algorithms to isolate the Doppler effect from the raw spectral signal.However,direct deconvolution becomes invalid in the presence of noise as it leads to infinite amplification of high-frequency noise components.To address this issue,we propose a deconvolution algorithm based on the maximum entropy principle.We validate the effectiveness of the proposed algorithm by utilizing simulated LIF spectra at various noise levels(signal-to-noise ratio,SNR=20–80 d B)and measured LIF spectra with Xe as the working fluid.In the typical measured spectrum(SNR=26.23 d B)experiment,compared with the Gaussian filter and the Richardson–Lucy(R-L)algorithm,the proposed algorithm demonstrates an increase in SNR of 1.39 d B and 4.66 d B,respectively,along with a reduction in the root-meansquare error(RMSE)of 35%and 64%,respectively.Additionally,there is a decrease in the spectral angle(SA)of 0.05 and 0.11,respectively.In the high-quality spectrum(SNR=43.96 d B)experiment,the results show that the running time of the proposed algorithm is reduced by about98%compared with the R-L iterative algorithm.Moreover,the maximum entropy algorithm avoids parameter optimization settings and is more suitable for automatic implementation.In conclusion,the proposed algorithm can accurately resolve Doppler spectrum details while effectively suppressing noise,thus highlighting its advantage in LIF spectral deconvolution applications.展开更多
Laser-induced fluorescence excitation spectra of jet-cooled NiS molecules were recorded in the energy range of 12200-13550 cm^-1. Four vibronic bands with rotational structure have been observed and assigned to the [1...Laser-induced fluorescence excitation spectra of jet-cooled NiS molecules were recorded in the energy range of 12200-13550 cm^-1. Four vibronic bands with rotational structure have been observed and assigned to the [12.4]^3∑-0-X^3∑0 transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.展开更多
We have reinvestigated the B-X and C-X band systems of CuCl by recording the laser- induced fluorescence excitation spectra in 20400-21800 cm^-1. The rotational analyses in Hund＇s case （a） revealed unambiguously a ...We have reinvestigated the B-X and C-X band systems of CuCl by recording the laser- induced fluorescence excitation spectra in 20400-21800 cm^-1. The rotational analyses in Hund＇s case （a） revealed unambiguously a singlet-to-singlet transition nature. The radiative lifetimes were measured to be 4.670 and 4.667 μs, respectively, which are much longer than that expected for a pure singlet of CuCl. This implies that the fluorescence mechanism in the B or C band systems lies in the mixing of the singlets （^1II and ^1E^＋） and triplets （^3II0,1,2） and that the two excited states observed in our experiment might be the singlets that have been strongly ＂contaminated＂ by their triplet neighbors.展开更多
Laser-induced fluorescence excitation spectra of jet-cooled CoS molecules have been recorded in the energy range of 15200-19000 cm^-1. Five transition progressions have been reported for the first time, the assignment...Laser-induced fluorescence excitation spectra of jet-cooled CoS molecules have been recorded in the energy range of 15200-19000 cm^-1. Five transition progressions have been reported for the first time, the assignments of these progressions have been derived from a rotational analysis of vibronic bands and they are determined to be [15.58]^4△7/2-X^4△7/2, [16.02]^4△7/2- X^4△7/2, [16.50]^4△7/2-X^4△T/2, [17.80]^4II5/2-X^4△7/2, and [18.00]^4△7/2-X^4△7/2 transitions. In addition, under the supersonic jet condition the fluorescent lifetimes of these vibronic states were measured by exponentially fitting the fluorescence decay. Based on the observed spectra and the measured lifetimes of the vibronic states, the newly identified electronic states are discussed.展开更多
The laser-induced fluorescence excitation spectra of jet-cooled NiB radicals have been recorded in the energy range of 19000-22100 cm-1. Eleven bands have been assigned to the [20.77]2П-X2∑＋ transition system for t...The laser-induced fluorescence excitation spectra of jet-cooled NiB radicals have been recorded in the energy range of 19000-22100 cm-1. Eleven bands have been assigned to the [20.77]2П-X2∑＋ transition system for the first time. The dispersed fluorescence spectra related to most of these bands have been investigated. Vibrationally excited levels of the ground electronic state, with v＂ up to 6, have been observed. In addition, the lifetimes for almost all the observed bands have also been measured.展开更多
The one-dimensional （1D） spatial distributions of OH absolute concentration in methane/air laminar premixed flat flame under different equivalence ratios at atmospheric pressure are investigated by using bi-directio...The one-dimensional （1D） spatial distributions of OH absolute concentration in methane/air laminar premixed flat flame under different equivalence ratios at atmospheric pressure are investigated by using bi-directional laser-induced flu- orescence （LIF） detection scheme combined with the direct absorption spectroscopy. The effective peak absorption cross section and the average temperature at a height of 2 mm above the burner are obtained by exciting absorption on the Q1（8） rotational line in the A2∑＋ （Dt = 0） ←- X2∏ （v = 0） at 309.240 nm. The measured values are 1.86×10-15 cm2 and 1719 K, respectively. Spatial filtering and frequency filtering methods of reducing noise are used to deal with the experi- mental data, and the smoothing effects are also compared using the two methods. The spatial distribution regularities of OH concentration are obtained with the equivalence ratios ranging from 0.8 to 1.3. The spatial resolution of the measured result is 84μm. Finally, a comparison is made between the experimental result of this paper and other relevant study results.展开更多
Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in therm...Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.展开更多
An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar ...An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.展开更多
To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of ...To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.展开更多
The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF（laserinduced fluorescence） in flame.The detailed physical models of spectral absorption lineshape broadening,c...The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF（laserinduced fluorescence） in flame.The detailed physical models of spectral absorption lineshape broadening,collisional transition and quenching at elevated pressure are built.The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation,which include collisional quenching,rotational energy transfer（RET）,and vibrational energy transfer（VET）.Based on these,some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure.These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor.展开更多
In this paper the OH radicals produced by a needle-plate negative DC discharge in water vapor,N_(2)+H_(2)O mixture gas and He+H_(2)O mixture gas are investigated by a laser-induced fluorescence(LIF)system.With a balla...In this paper the OH radicals produced by a needle-plate negative DC discharge in water vapor,N_(2)+H_(2)O mixture gas and He+H_(2)O mixture gas are investigated by a laser-induced fluorescence(LIF)system.With a ballast resistor in the circuit,the discharge current is limited and the discharges remain in glow.The OH rotation temperature is obtained from fluorescence rotational branch fitting,and is about 350 K in pure water vapor.The effects of the discharge current and gas pressure on the production and quenching processes of OH radicals are investigated.The results show that in water vapor and He+H_(2)O mixture gas the fluorescence intensity of OH stays nearly constant with increasing discharge current,and in N_(2)+H_(2)O mixture gas the fluorescence intensity of OH increases with increasing discharge current.In water vapor and N_(2)+H_(2)O mixture gas the fluorescence intensity of OH decreases with increasing gas pressure in the studied pressure range,and in He+H_(2)O mixture gas the fluorescence intensity of OH shows a maximum value within the studied gas pressure range.The physicochemical reactions between electrons,radicals,ground and metastable molecules are discussed.The results in this work contribute to the optimization of plasma reactivity and the establishment of a molecule reaction dynamics model.展开更多
A semi-analytical Monte Carlo (SMC) simulation was developed to simulate the propagation of laser-induced fluo- rescence (LIF) in an optically participating spray, which simultaneously exhibits spectrally dependent em...A semi-analytical Monte Carlo (SMC) simulation was developed to simulate the propagation of laser-induced fluo- rescence (LIF) in an optically participating spray, which simultaneously exhibits spectrally dependent emission, anisotropic scattering, absorption, and re-emission. The SMC simulation is described and then applied to an experimental configuration of a cloud of polydisperse droplets composed of water and sulforhodamine B dye. In the SMC simulation, the collected LIF flux on the remote receptor element is calculated as the global contribution from the emissive source, single, twice, … and nth collision events in any sequence. The effects on the fluorescence photons propagation of spray parameters like the dye concentration, droplets concentration, and droplets size are examined. Three spectral bands representing different optical properties are chosen to analyze the interference of absorption, scattering and re-emission on the detected LIF flux. The obtained spectral LIF flux distribution on the receptor demonstrates a “red shift” phenomenon.展开更多
A combined detection system involving simultaneous LIF and contacfless-conductometric measurements at the same place of the microfluidic chip was described. The LIF measurement was designed according to the confocal p...A combined detection system involving simultaneous LIF and contacfless-conductometric measurements at the same place of the microfluidic chip was described. The LIF measurement was designed according to the confocal principle and a moveable contactless-conduetivity detector was used in C^4D. Both measurements were mutually independent and advantageous in analyses of mixtures. Various experimental parameters affecting the response were examined and optimized. The performances were demonstrated by simultaneous detection of Rhodamine B. And the results showed that the combined detection system could be used sensitively and reliably.展开更多
The absolute number density of nitrogen dioxide（NO2） seeded in argon is measured with cavity-enhanced laserinduced fluorescence（CELIF） through using a pulsed laser beam for the first time. The cavity ring down（CR...The absolute number density of nitrogen dioxide（NO2） seeded in argon is measured with cavity-enhanced laserinduced fluorescence（CELIF） through using a pulsed laser beam for the first time. The cavity ring down（CRD） signal is acquired simultaneously and used for normalizing the LIF signal and determining the relationship between the measured CELIF signal and the NO2 number density. The minimum detectable NO2 density down to（3.6±0.1）10^8 cm^-3 is measured in 60 s of acquisition time by the CELIF method. The minimum absorption coefficient is measured to be（2.0±0.1）10^-9 cm^-1, corresponding to a noise equivalent absorption sensitivity of（2.2±0.1）10^9 cm.^-1Hz^-1/2. The experimental system demonstrated here can be further improved in its sensitivity and used for environmental monitoring of outdoor NO2 pollution.展开更多
Laser-induced fluorescence excitation spectra and dispersed fluorescence spectra of cobalt sulfide （COS） have been recorded in the energy range of 22400-24400 cm-1 （corresponding to 446-409 nm）. A new electronic t...Laser-induced fluorescence excitation spectra and dispersed fluorescence spectra of cobalt sulfide （COS） have been recorded in the energy range of 22400-24400 cm-1 （corresponding to 446-409 nm）. A new electronic transition progression with six vibronic bands, stemming from the X4AT/2 state of CoS, was identified and assigned to be [24.0014AT/2-X4A7/2. The new observed 4A state most probably originates from the core[10a2][47r3][lla2][153][57r3] electronic configuration. Strong perturbations are found to extensively exist in the transition bands of this new state. The rotational constants and lifetimes of these bands have been determined.展开更多
Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally anal...Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally analyzed to determine the molecular constants. The excited states exhibit highly irregular variations in terms of isotopic shifts, vibrational intervals, and rotational constants. Twenty-six bands attributed to [Ω=0, 1]-X3∑o transitions have been tentatively grouped into five vibrational progressions. Furthermore, dispersed fluorescence and lifetimes of the strong bands have also been measured.展开更多
An automatic system for marine meiobenthos separation was developed by using laser-induced fluorescence tech- nology. Rose Bengal was used as organism dye and the spectrums of Rose Bengal were measured. Laser-induced ...An automatic system for marine meiobenthos separation was developed by using laser-induced fluorescence tech- nology. Rose Bengal was used as organism dye and the spectrums of Rose Bengal were measured. Laser-induced fluorescence system was established to detect marine meiobenthos in sediments. Data obtained from experiments were analyzed by using a mathematical model. The results showed that laser-induced fluorescence technology worked well in the system. The system could select the meiobenthos efficiently and precisely.展开更多
The effects of temperature and pressure on laser-induced fluorescence(LIF)of OH are numerically studied under the excitation of A-X(1,0)transition at high pressures.A detailed theoretical analysis is carried out to re...The effects of temperature and pressure on laser-induced fluorescence(LIF)of OH are numerically studied under the excitation of A-X(1,0)transition at high pressures.A detailed theoretical analysis is carried out to reveal the physical processes of LIF.It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure-and temperature-dependent parameters,such as Boltzmann fraction,absorption lineshape broadening,central-frequency shifting,and collisional quenching.Operations at high pressures require a careful choice of an excitation line,and the Q1(8)line in the A-X(1,0)band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction.The absorption spectra of OH become much broader as pressure increases,leading to a smaller overlap integral and thus smaller excitation efficiency.The central-frequency shifting cannot be omitted at high pressures,and should be taken into account when setting the excitation frequency.The fluorescence yield is estimated based on the LASKIN calculation.Finally,OH-LIF measurements were conducted on flat stoichiometric CH4/air flames at high pressures.And both the numerical and experimental results illustrate that the pressure dependence of fluorescence yield is dominated,and the fluorescence yield is approximately inversely proportional to pressure.These results illustrate the physical processes of OH-LIF and provide useful guidelines for high-pressure application of OH-LIF.展开更多
Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13...Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13.0]2II3/2（v＇=0-5）-X2II3/2（v＂=0） transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.展开更多
The laser-induced fluorescence excitation spectrum of jet-cooled NiS molecule has been recorded in the energy range of 15500 17200 cm-1. Fifteen bands have been assigned as three transition progressions：[15.65]^3Ⅱ1...The laser-induced fluorescence excitation spectrum of jet-cooled NiS molecule has been recorded in the energy range of 15500 17200 cm-1. Fifteen bands have been assigned as three transition progressions：[15.65]^3Ⅱ1（v′=0-4）-X^3∑0^-（v″=0）,[15.69]^3∑0^-（v′=0-4）-X^3∑0^-（v″=0）,and [15.81]^3Ⅱ1（v′=0-4）-X^3∑0^-（v″=0）.Spectroscopic constants for the three newly identified electronically excited states have been determined for the first time. In addition,the lifetimes for most observed vibronic bands have also been measured.展开更多
文摘Laser-induced fluorescence(LIF)spectroscopy is employed for plasma diagnosis,necessitating the utilization of deconvolution algorithms to isolate the Doppler effect from the raw spectral signal.However,direct deconvolution becomes invalid in the presence of noise as it leads to infinite amplification of high-frequency noise components.To address this issue,we propose a deconvolution algorithm based on the maximum entropy principle.We validate the effectiveness of the proposed algorithm by utilizing simulated LIF spectra at various noise levels(signal-to-noise ratio,SNR=20–80 d B)and measured LIF spectra with Xe as the working fluid.In the typical measured spectrum(SNR=26.23 d B)experiment,compared with the Gaussian filter and the Richardson–Lucy(R-L)algorithm,the proposed algorithm demonstrates an increase in SNR of 1.39 d B and 4.66 d B,respectively,along with a reduction in the root-meansquare error(RMSE)of 35%and 64%,respectively.Additionally,there is a decrease in the spectral angle(SA)of 0.05 and 0.11,respectively.In the high-quality spectrum(SNR=43.96 d B)experiment,the results show that the running time of the proposed algorithm is reduced by about98%compared with the R-L iterative algorithm.Moreover,the maximum entropy algorithm avoids parameter optimization settings and is more suitable for automatic implementation.In conclusion,the proposed algorithm can accurately resolve Doppler spectrum details while effectively suppressing noise,thus highlighting its advantage in LIF spectral deconvolution applications.
基金This work was supported by the National Natural Science Foundation of China （No.21273212 and No.21173205）, the National Key Basic Research Program of China （No.2010CB923302）, the Chinese Academy of Sciences （No.KJCX2-YW-N24）, the Fundamental Research Funds for the Central Universities of China （No.WK2340000012）, and the University of Science and Technology of China-National Synchrotron Radiation Laboratory （No.KY2340000021）.
文摘Laser-induced fluorescence excitation spectra of jet-cooled NiS molecules were recorded in the energy range of 12200-13550 cm^-1. Four vibronic bands with rotational structure have been observed and assigned to the [12.4]^3∑-0-X^3∑0 transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.
文摘We have reinvestigated the B-X and C-X band systems of CuCl by recording the laser- induced fluorescence excitation spectra in 20400-21800 cm^-1. The rotational analyses in Hund＇s case （a） revealed unambiguously a singlet-to-singlet transition nature. The radiative lifetimes were measured to be 4.670 and 4.667 μs, respectively, which are much longer than that expected for a pure singlet of CuCl. This implies that the fluorescence mechanism in the B or C band systems lies in the mixing of the singlets （^1II and ^1E^＋） and triplets （^3II0,1,2） and that the two excited states observed in our experiment might be the singlets that have been strongly ＂contaminated＂ by their triplet neighbors.
文摘Laser-induced fluorescence excitation spectra of jet-cooled CoS molecules have been recorded in the energy range of 15200-19000 cm^-1. Five transition progressions have been reported for the first time, the assignments of these progressions have been derived from a rotational analysis of vibronic bands and they are determined to be [15.58]^4△7/2-X^4△7/2, [16.02]^4△7/2- X^4△7/2, [16.50]^4△7/2-X^4△T/2, [17.80]^4II5/2-X^4△7/2, and [18.00]^4△7/2-X^4△7/2 transitions. In addition, under the supersonic jet condition the fluorescent lifetimes of these vibronic states were measured by exponentially fitting the fluorescence decay. Based on the observed spectra and the measured lifetimes of the vibronic states, the newly identified electronic states are discussed.
文摘The laser-induced fluorescence excitation spectra of jet-cooled NiB radicals have been recorded in the energy range of 19000-22100 cm-1. Eleven bands have been assigned to the [20.77]2П-X2∑＋ transition system for the first time. The dispersed fluorescence spectra related to most of these bands have been investigated. Vibrationally excited levels of the ground electronic state, with v＂ up to 6, have been observed. In addition, the lifetimes for almost all the observed bands have also been measured.
基金supported by the National Key Scientific Instrument and Equipment Development Projects of China(Grant No.2012YQ040164)the National Natural Science Foundation of China(Grant Nos.61275127 and 91441130)+1 种基金the China Postdoctoral Science Foundation(Grant No.2014M560262)the Postdoctoral Fellowship in Heilongjiang Province,China(Grant No.LBH-Z14074)
文摘The one-dimensional （1D） spatial distributions of OH absolute concentration in methane/air laminar premixed flat flame under different equivalence ratios at atmospheric pressure are investigated by using bi-directional laser-induced flu- orescence （LIF） detection scheme combined with the direct absorption spectroscopy. The effective peak absorption cross section and the average temperature at a height of 2 mm above the burner are obtained by exciting absorption on the Q1（8） rotational line in the A2∑＋ （Dt = 0） ←- X2∏ （v = 0） at 309.240 nm. The measured values are 1.86×10-15 cm2 and 1719 K, respectively. Spatial filtering and frequency filtering methods of reducing noise are used to deal with the experi- mental data, and the smoothing effects are also compared using the two methods. The spatial distribution regularities of OH concentration are obtained with the equivalence ratios ranging from 0.8 to 1.3. The spatial resolution of the measured result is 84μm. Finally, a comparison is made between the experimental result of this paper and other relevant study results.
基金supported by National Energy R&D Center of Petroleum Refining Technology of China(RIPP,SINOPEC)National Key Research and Development Program of China(No.2017YFA0304203)+5 种基金Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT_17R70)National Natural Science Foundation of China(Nos.61975103,61875108,61775125 and 11434007)Industrial Application Innovation Project(No.627010407)Scientific and Technological Innovation Project of Shanxi Gemeng US-China Clean Energy R&D Center Co.,Ltd111 Project(D18001)Fund for Shanxi‘1331KSC’。
文摘Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.
基金supported by the National Natural Science Foundation of China(Grant No.11272338)the Science and Technology on Scramjet Key Laboratory Funding,China(Grant No.STSKFKT 2013004)the China Scholarship Council
文摘An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51536002,61405048,and 91441130)。
文摘To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.
基金Project supported by the National Natural Science Foundation of China(Grant No.11272338)the Fund from the Science and Technology on Scramjet Key Laboratory,China(Grant No.STSKFKT2013004)
文摘The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF（laserinduced fluorescence） in flame.The detailed physical models of spectral absorption lineshape broadening,collisional transition and quenching at elevated pressure are built.The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation,which include collisional quenching,rotational energy transfer（RET）,and vibrational energy transfer（VET）.Based on these,some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure.These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor.
基金supported by National Natural Science Foundation of China(No.51777091)Innovative Talents Team Project of‘Six Talent Peaks’of Jiangsu Province(No.TDJNHB-006)Postgraduate Research&Practice Innovation Program of Jiangsu Province in China(No.SJCX20_0345)。
文摘In this paper the OH radicals produced by a needle-plate negative DC discharge in water vapor,N_(2)+H_(2)O mixture gas and He+H_(2)O mixture gas are investigated by a laser-induced fluorescence(LIF)system.With a ballast resistor in the circuit,the discharge current is limited and the discharges remain in glow.The OH rotation temperature is obtained from fluorescence rotational branch fitting,and is about 350 K in pure water vapor.The effects of the discharge current and gas pressure on the production and quenching processes of OH radicals are investigated.The results show that in water vapor and He+H_(2)O mixture gas the fluorescence intensity of OH stays nearly constant with increasing discharge current,and in N_(2)+H_(2)O mixture gas the fluorescence intensity of OH increases with increasing discharge current.In water vapor and N_(2)+H_(2)O mixture gas the fluorescence intensity of OH decreases with increasing gas pressure in the studied pressure range,and in He+H_(2)O mixture gas the fluorescence intensity of OH shows a maximum value within the studied gas pressure range.The physicochemical reactions between electrons,radicals,ground and metastable molecules are discussed.The results in this work contribute to the optimization of plasma reactivity and the establishment of a molecule reaction dynamics model.
基金Project supported by the National Natural Science Foundation of China (No. 60534030)the Scholarship of French Embassy in China and the Doctoral Grant from French Embassy in China
文摘A semi-analytical Monte Carlo (SMC) simulation was developed to simulate the propagation of laser-induced fluo- rescence (LIF) in an optically participating spray, which simultaneously exhibits spectrally dependent emission, anisotropic scattering, absorption, and re-emission. The SMC simulation is described and then applied to an experimental configuration of a cloud of polydisperse droplets composed of water and sulforhodamine B dye. In the SMC simulation, the collected LIF flux on the remote receptor element is calculated as the global contribution from the emissive source, single, twice, … and nth collision events in any sequence. The effects on the fluorescence photons propagation of spray parameters like the dye concentration, droplets concentration, and droplets size are examined. Three spectral bands representing different optical properties are chosen to analyze the interference of absorption, scattering and re-emission on the detected LIF flux. The obtained spectral LIF flux distribution on the receptor demonstrates a “red shift” phenomenon.
文摘A combined detection system involving simultaneous LIF and contacfless-conductometric measurements at the same place of the microfluidic chip was described. The LIF measurement was designed according to the confocal principle and a moveable contactless-conduetivity detector was used in C^4D. Both measurements were mutually independent and advantageous in analyses of mixtures. Various experimental parameters affecting the response were examined and optimized. The performances were demonstrated by simultaneous detection of Rhodamine B. And the results showed that the combined detection system could be used sensitively and reliably.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504112,91536218,and 11604100)
文摘The absolute number density of nitrogen dioxide（NO2） seeded in argon is measured with cavity-enhanced laserinduced fluorescence（CELIF） through using a pulsed laser beam for the first time. The cavity ring down（CRD） signal is acquired simultaneously and used for normalizing the LIF signal and determining the relationship between the measured CELIF signal and the NO2 number density. The minimum detectable NO2 density down to（3.6±0.1）10^8 cm^-3 is measured in 60 s of acquisition time by the CELIF method. The minimum absorption coefficient is measured to be（2.0±0.1）10^-9 cm^-1, corresponding to a noise equivalent absorption sensitivity of（2.2±0.1）10^9 cm.^-1Hz^-1/2. The experimental system demonstrated here can be further improved in its sensitivity and used for environmental monitoring of outdoor NO2 pollution.
文摘Laser-induced fluorescence excitation spectra and dispersed fluorescence spectra of cobalt sulfide （COS） have been recorded in the energy range of 22400-24400 cm-1 （corresponding to 446-409 nm）. A new electronic transition progression with six vibronic bands, stemming from the X4AT/2 state of CoS, was identified and assigned to be [24.0014AT/2-X4A7/2. The new observed 4A state most probably originates from the core[10a2][47r3][lla2][153][57r3] electronic configuration. Strong perturbations are found to extensively exist in the transition bands of this new state. The rotational constants and lifetimes of these bands have been determined.
文摘Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally analyzed to determine the molecular constants. The excited states exhibit highly irregular variations in terms of isotopic shifts, vibrational intervals, and rotational constants. Twenty-six bands attributed to [Ω=0, 1]-X3∑o transitions have been tentatively grouped into five vibrational progressions. Furthermore, dispersed fluorescence and lifetimes of the strong bands have also been measured.
基金Project (Grant No. DY105-03-01-15) supported by "Tenth FiveYear Plan of R & D of International Deep-Sea" of National OceanMineral Resources R & D Association, China
文摘An automatic system for marine meiobenthos separation was developed by using laser-induced fluorescence tech- nology. Rose Bengal was used as organism dye and the spectrums of Rose Bengal were measured. Laser-induced fluorescence system was established to detect marine meiobenthos in sediments. Data obtained from experiments were analyzed by using a mathematical model. The results showed that laser-induced fluorescence technology worked well in the system. The system could select the meiobenthos efficiently and precisely.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51976233 and 91641118).
文摘The effects of temperature and pressure on laser-induced fluorescence(LIF)of OH are numerically studied under the excitation of A-X(1,0)transition at high pressures.A detailed theoretical analysis is carried out to reveal the physical processes of LIF.It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure-and temperature-dependent parameters,such as Boltzmann fraction,absorption lineshape broadening,central-frequency shifting,and collisional quenching.Operations at high pressures require a careful choice of an excitation line,and the Q1(8)line in the A-X(1,0)band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction.The absorption spectra of OH become much broader as pressure increases,leading to a smaller overlap integral and thus smaller excitation efficiency.The central-frequency shifting cannot be omitted at high pressures,and should be taken into account when setting the excitation frequency.The fluorescence yield is estimated based on the LASKIN calculation.Finally,OH-LIF measurements were conducted on flat stoichiometric CH4/air flames at high pressures.And both the numerical and experimental results illustrate that the pressure dependence of fluorescence yield is dominated,and the fluorescence yield is approximately inversely proportional to pressure.These results illustrate the physical processes of OH-LIF and provide useful guidelines for high-pressure application of OH-LIF.
基金This work was supported by the National Natural Science Foundation of China （No.21273212, No.20873133, and No.21173205）, the National Key Basic Research Program of China （No.2010CB923302）, the Chinese Academy of Sciences （No.KJCX2-YW-N24）, the FRFCUC （No.WK2340000012）, and the USTC-NSRL Joint Funds （No.KY2340000021）.
文摘Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13.0]2II3/2（v＇=0-5）-X2II3/2（v＂=0） transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20673107）, the National Key Basic Research Special Foundation of China （No.G2007CB815203）, and the Chinese Academy of Sciences （No.KJCX2-YW-N24）.
文摘The laser-induced fluorescence excitation spectrum of jet-cooled NiS molecule has been recorded in the energy range of 15500 17200 cm-1. Fifteen bands have been assigned as three transition progressions：[15.65]^3Ⅱ1（v′=0-4）-X^3∑0^-（v″=0）,[15.69]^3∑0^-（v′=0-4）-X^3∑0^-（v″=0）,and [15.81]^3Ⅱ1（v′=0-4）-X^3∑0^-（v″=0）.Spectroscopic constants for the three newly identified electronically excited states have been determined for the first time. In addition,the lifetimes for most observed vibronic bands have also been measured.
