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Express: Modelling of Carbon Monoxide Two-Photon Laser-Induced Fluorescence (LIF) Spectra at High Temperature and Pressure
摘要： In this study, quantitative model of two-photon excitation and fluorescence spectra of carbon monoxide based on up-to-date spectroscopic constants collected during an extensive literature survey was developed. This semi-classical model takes into account H?nl–London factors, quenching effects (collisional broadening and shift), ionization and stark effect (broadening and shift), whereas predissociation is neglected. It was specifically developed to first reproduce with a high confidence level the behavior of our experimental spectra obtained from laser-induced fluorescence (LIF) measurements, and then to allow us to extrapolate the fluorescence signal amplitude in other conditions than those used in these experiments. Synthetic two-photon excitation and fluorescence spectra of CO were calculated to predict the fluorescence signal at high pressures and temperatures, which are representative of gas turbine operating conditions. Comparison between experimental and calculated spectra is presented. Influence of temperature on both excitation and fluorescence spectra shapes and amplitudes is well reproduced by the simulated ones. It is then possible to estimate flame temperature from the comparison between experimental and calculated shapes of numerical excitation spectra. Influence of pressure on both excitation and fluorescence spectra was also investigated. Results show that for temperature below 600 K and pressure above 0.1 MPa, the usual Voigt profile is not suitable to reproduce the shape of the excitation spectrum. We found that the Lindholm profile is well suited to reproduce the pressure-dependence of the spectrum in the range 0.1 to 0.5 MPa at 300 K, and 0.1 to 0.7 MPa at 860 K. Beyond 0.7 MPa, in this temperature range, it is shown that the Lindholm profile does no longer match the spectral profiles, in particularly the red wing. Further analyses taking into account the line mixing phenomenon at higher pressure are thus discussed.
关键词： spectroscopy,combustion,modeling,LIF,Laser-induced fluorescence,carbon monoxide
更新于2025-09-19 17:13:59
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Precise near-wall pH measurement in pressure-driven and electrically-driven flows using nanoscale laser-induced fluorescence imaging
摘要： The present study developed a near-wall pH measurement technique based on nanoscale laser-induced fluorescence to evaluate the spatio-temporal distributions of pH in the vicinity of a glass-solution interface. Fluorescein sodium salt, a pH-sensitive dye, was dissolved in working fluids and excited by an evanescent wave generated by total internal reflection of a laser beam. Near-wall pH distributions were determined based on a ratiometric calibration using a high-pH buffer solution (pH ? 10) as a reference. The proposed technique was applied to both pressure-driven and electroosmotic flows to investigate the effects of interfacial potential and external electric field on proton concentration. The near-wall pH in pressure-driven flow was lower than the bulk pH by ~0.2 due to the local excess of protons attracted towards the negatively charged glass wall. This pH shift was especially noticeable in solutions with low ionic strength, which indicates that the near-wall pH is closely related to the thickness of the electric double layer. The pH shift in electroosmotic flow was smaller than that in pressure-driven flow by ~0.02 and decreased with electric field strength. In addition, a time-series measurement clearly visualized the temporal change in non-uniform pH distributions in electroosmotic flow at a spatial resolution of 5.2 × 5.2 μm. The measurement uncertainty was estimated to be 0.16 pH unit at 95% confidence level. These results demonstrated the feasibility of the present technique to evaluate spatio-temporal proton concentrations within the space 10–100 nm away from a solid–liquid interface. The proposed technique will therefore contribute to quantitative investigations into electrostatic interactions and ion transport in developing nanoscale electrochemical transport techniques and devices in, for example, biochemical analysis and water purification.
关键词： liquid–solid interface,laser-induced fluorescence,proton concentration,electric double layer,evanescent wave,electroosmotic flow,pH measurement
更新于2025-09-19 17:13:59
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Discrimination between fresh, chilled, and frozen/thawed chicken based on its skin's spectrochemical and optical properties
摘要： Monitoring of the spectrochemical and optical properties of biomaterials has been widely utilized in many biomedical applications for both diagnosis and therapy. Recently, these nondestructive, noninvasive technologies have been used to inspect the quality and safety of food products. In this work, samples from chicken breast skin were investigated spectrochemically and optically to distinguish between fresh, frozen/thawed, and chilled chicken to reveal the adulteration of fresh meat and commercial fraud. Spectrochemical analysis was carried out using the Laser-Induced Fluorescence (LIF) technique. In the LIF setup used, a diode-pumped solid-state laser was used as a pump laser at l ? 266 nm. The LIF spectra were then analyzed statistically using the principal component analysis (PCA) method, while optical analysis was conducted via measurement of the parameters of the absorption and scattering of laser light (l ? 405 nm) on the chicken's skin. The optical absorption and scattering coe?cients were acquired using an integrating sphere with a combination of the Beer–Lambert law and the Kubelka–Munk mathematical model. The spatial distribution of light at the sample surface was modeled using Monte-Carlo simulation and ?nite element solution of the di?usion equation to visualize the results. The potential of the LIF technique combined with principal component analysis in discriminating between the three chicken categories was validated by measuring the optical parameters as well as the simulation model. Besides, the discriminative ability of the proposed method was evaluated using receiver operating characteristic (ROC) curves, which showed sensitivity in discriminating fresh and frozen samples of 0.82 and 0.74 in fresh-chilled separation. These investigations demonstrate the capability of using LIF and proper software for in situ commercial fraud detection, i.e., in supermarkets and/or meat supplier centers.
关键词： Laser-Induced Fluorescence,Chicken meat quality,Optical properties,Commercial fraud detection,Principal Component Analysis
更新于2025-09-19 17:13:59
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Multivariate determination of 10B isotopic ratio by laser-induced breakdown spectroscopy using multiple BO molecular emissions
摘要： Measurements of boron isotopic ratios have been investigated using LIBS, and combined LIBS and Molecular laser-induced fluorescence (MLIF). Mixtures of various ratios of research grade H3 11BO3 and H3 10BO3 in pellet form were interrogated with a Q-switched Nd:YAG laser operating at 532 nm. The resulting plasma was examined for their BO molecular bands in the 254–262 nm and 266–276 nm wavelength ranges. A minimum of three band heads of the β system B2Σ → X2Σ transitions were identified. The rovibronic isotopic shifts of the corresponding bands were measured and were conclusively compared to the literature. MLIF was applied to LIBS emission lines covering 253–271 nm to enhance some band heads, selectively. Both LIBS and LIBS-MLIF emissions were subject to multivariate statistical analysis to predict 10B isotopic ratios. Two PLS regression calibration models were examined to better examine the effects, sensitivity, accuracy of the laser-produced plasma excitation modalities based models through the figure of merit. For the full calibration set (21 samples), the root mean square error of cross-validation (RMSECV), the pseudo univariate LOD (LODpu) and the LOD interval ([LODmin, LODmax]) for 10B isotopes were improved from 1.61%, 4.81%, [2.64%, 3.49%] 10B isotopic ratio, respectively for LIBS to 0.98%, 2.40%, [2.19%, 2.81%] 10B isotopic ratio, respectively for LIBS-MLIF. However, using a random subset of the samples (14) as a calibration set and the rest as a test set, the root mean square error of prediction of 10B isotopic ratio in the test set improved from 2.95% to 1.16% 10B isotopic ratio, respectively for LIBS and LIBS-MLIF; and the LOD interval improved from [2.45%, 2.69%] to [1.88%, 2.12%] 10B isotopic ratio when calculated with cross-validated residual variance. Moreover, the prediction error of a test set improved from 2.95% for LIBS to 1.16% for LIBS-MLIF.
关键词： Molecular laser-induced fluorescence,LIBS-MLIF,Limit of detection interval,Laser-induced breakdown spectroscopy,Boron isotopes,Molecular band
更新于2025-09-16 10:30:52
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Laser-induced fluorescence of helium ions in ITER divertor
摘要： Laser-induced fluorescence (LIF) on ITER will be used for local measurement of helium density nHe and ion temperature Ti in divertor. The LIF diagnostic is combined with the divertor Thomson scattering (DTS) via common laser injection and signal collection optics. Collisional-radiative model developed for helium ions is used to estimate laser parameters required for robust measurement of laser-induced signals against plasma background radiation. The estimations demonstrate feasibility of measuring nHeII with laser parameters provided by available optical parametric oscillator pumped by Nd:YAG. New approach for measuring Ti is proposed and the expected errors are estimated using numerical simulations.
关键词： Helium density,ITER,Laser-induced quenching,Laser-induced fluorescence,Ion temperature,Divertor
更新于2025-09-16 10:30:52
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Temperature dependence of the parameters of laser-induced fluorescence and species composition of phytoplankton: The theory and the experiments
摘要： The article discusses the opportunity to determine the species composition of a mixture of microalgae by using the temperature dependence of their laser-induced fluorescence (LIF). Experimental temperature dependences of fluorescence were obtained for the following microalgae: Picochlorum maculatum, Dunaliella salina, Chlorella minutissima, Tetraselmis viridis, Porphyridium purpureum, and Rhodomonas salina. It has been shown that the temperature dependence of fluorescence intensity of chlorophyll a in microalgae is reflective of the specific processes in cells of different microalgae species. A mathematical model for the temperature dependence of microalgae fluorescence and its relationship with the processes occurring in microalgae cells when heated has been formulated. The model allows determining the composition of mixtures with sufficient accuracy, as was shown experimentally on test mixtures of microalgae cultures.
关键词： Temperature dependence of fluorescence intensity,Phytoplankton,Chlorophyll a,Laser-induced fluorescence
更新于2025-09-16 10:30:52
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Fluorescence and Time-Delayed Lasing during Single Laser Pulse Excitation of a Pendant mm-Sized Dye Droplet
摘要： Fluorescence and lasing emission that are produced separately in time during excitation laser pulse for an mm-sized Rhodamine 6G dye-water droplet are reported. The droplet acts as a quasi-spherical closed optical resonator and due to multiple internal reflections, the resonant amplified emission is delayed with respect to fluorescence emission. Measurements of the temporal evolution of the droplet’s emission were performed by varying the signal acquisition gate width and gate delay with respect to the pumping pulse. The droplet emission spectra are structured in two bands which appear one after the other in time: first, the fluorescence emission band which follows pumping laser pulse time shape and then a second band, the lasing band, placed at shorter wavelengths and formed in time after the peak of the pumping laser pulse intensity, on the pulse tail. The lasing threshold pumping intensity is much lower than those for typical dye lasers.
关键词： optical signal sampling,laser dye,mm-sized droplets,lasing,laser-induced fluorescence
更新于2025-09-16 10:30:52
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Instantaneous one-dimensional ammonia measurements with femtosecond two-photon laser-induced fluorescence (fs-TPLIF)
摘要： Ammonia (NH3) has been identified as a potential hydrogen-carrier fuel with no carbon emissions. Non-intrusive in-situ NH3 diagnostic technique is of great interest. In this work, femtosecond two-photon laser-induced fluorescence (fs-TPLIF) was demonstrated in NH3/N2 mixtures to achieve NH3 measurements. A femtosecond laser at 305 nm was used for two-photon excitation of NH3 to its excited state (XeC0), and the subsequent fluorescence at ~565 nm from transition C0-A was detected. In addition, a detection limit of 730 ppm was achieved in NH3/N2 mixtures. Furthermore, one-dimensional single-shot images of NH3 were obtained in both laminar and turbulent flow fields. This work is the first attempt of fs-TPLIF for polyatomic molecular gases measurements, and the obtained results indicate that fs-TPLIF could be a promising tool for NH3 measurements.
关键词： Laser-induced fluorescence,Femtosecond laser,Spectroscopy,Ammonia
更新于2025-09-16 10:30:52
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Analysis of the release kinetics of surface-bound proteins via laser-induced fluorescence
摘要： The drying and resolving processes of surface-bound proteins were analysed with a stereoscopic microscope combined with laser-induced fluorescence (LIF) with the aim to assist the advancement of a semi-automated point-of-care allergy diagnostic device. The results shown in this paper present the use of the LIF-method for concentration calibration and the analysis of drying and resolving dyed proteins. The method is established successfully and delivers precise results.
关键词： point-of-care testing (POCT),laser-induced fluorescence,spectroscopy,release kinetics
更新于2025-09-16 10:30:52
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[IEEE 2019 5th International Conference on Electric Power Equipment - Switching Technology (ICEPE-ST) - Kitakyushu, Japan (2019.10.13-2019.10.16)] 2019 5th International Conference on Electric Power Equipment - Switching Technology (ICEPE-ST) - Two-Dimensional Observation of Single Cathode Spot Copper Vapor in Vacuum Arcs by Laser-Induced Fluorescence
摘要： Vacuum arc cathode spots are centers of metal vapor evaporation, electron emission and plasma production. Arc properties are dominated by the behavior of the cathode spots. A systematic investigation on the density of copper metal vapor emitted from a single cathode spot is benefit for understanding the mechanism of vacuum arc discharge. The objective of this paper is to get the spatial density distribution of copper neutral atoms emitted from a single cathode spot in ~55A vacuum arc by planar Laser Induced Fluorescence (LIF) method. The experiments are conducted with CuCr10 (Cr weight of 10%) butt contacts in a demountable vacuum chamber. 2D distribution of copper metal vapor density is photographed by an intensified CCD cameral (i-CCD) with an exposure time of 50 ns. The uniform constant Axial Magnetic Field (AMF) within the inter-contacts region is supplied by Helmholtz coils. 2D copper vapor density distribution between two electrodes as well as the influence of external AMF on vapor density distribution are investigated. When the arc current is ~55 A, a typical cathode spot or two spots are observed in the experiments. Copper vapor density reaches the maximum value 6×1019 m-3 in the center of cathode spot.
关键词： Vacuum arc,Laser Induced Fluorescence,copper vapor density,cathode spots,Axial Magnetic Field
更新于2025-09-16 10:30:52