共查询到20条相似文献,搜索用时 15 毫秒
1.
Simultaneous photoacoustic detection of multiple compounds based on orthogonal functions stimulation
T. Starecki 《The European physical journal. Special topics》2008,153(1):435-437
The paper presents a concept of photoacoustic
measurements based on use of two different light wavelengths which
intensities are modulated with sine waves of the same frequency but with
phase difference of 90 degrees. Resultant photoacoustic signal is of the
same frequency, but its amplitude and phase depends on the absorption at
both wavelengths. Taking into consideration that sine and cosine are
orthogonal functions, and having measured amplitude of the photoacoustic
signal and its phase referred to the phase of the stimulating light
modulation, it is possible to retrieve both components corresponding to sine
and cosine modulation. As a result, the method can be applied to
simultaneous detection of two compounds. An important advantage of the
method is that it can be comfortably used with high Q-factor cells. 相似文献
2.
Time-resolved two-color LII: size distributions of nano-particles from gas-to-particle synthesis 总被引:1,自引:0,他引:1
Thilo Lehre Rainer Suntz Henning Bockhorn 《Proceedings of the Combustion Institute》2005,30(2):2585-2593
A two-color LII technique for in situ measurements of particle size distributions is described. The technique is based on the simultaneous detection of time-resolved LII signals at two different wavelengths with one-dimensional spatial resolution using a newly developed experimental setup. The ratio of both LII signals yields particle temperatures as a function of time and location. Measured particle temperature decays are numerically simulated based on a detailed cooling model for particle ensembles. Particle size distributions are obtained by fitting simulated particle temperature decays to measured ones using multi-dimensional non-linear regression. The two-color LII technique for particle sizing can be applied to a wide range of materials because it is independent of the optical properties of the particle material. Exemplarily, the measuring technique is applied to investigate the synthesis of nanoscaled metal oxide particle in a laser vaporization reactor. 相似文献
3.
《Optics Communications》1987,61(6):397-400
We report a new technique of generating highly synchronous simultaneous pulse trains at three wavelengths, two of which are continuously tunable over a moderate range. A series of oscillographs shows the time-resolved Ar+ pulses and the effects of varying the two cavity lengths with respect to each other. Preliminary correlation measurements indicate low jitter. 相似文献
4.
Bourquin S Prasankumar RP Kärtner FX Fujimoto JG Lasser T Salathé RP 《Optics letters》2003,28(17):1588-1590
A new femtosecond pump-probe spectroscopy technique is demonstrated that permits the high-speed, parallel acquisition of pump-probe measurements at multiple wavelengths. This is made possible by use of a novel, two-dimensional smart pixel detector array that performs amplitude demodulation in real time on each pixel. This detector array can not only achieve sensitivities comparable with lock-in amplification but also simultaneously performs demodulation of probe transmission signals at multiple wavelengths, thus permitting rapid time- and wavelength-resolved femtosecond pump-probe spectroscopy. Measurements on a thin sample of bulk GaAs are performed across 58 simultaneous wavelengths. Differential probe transmission changes as small as approximately 2 x 10(-4) can be measured over a 5-ps delay scan in only approximately 3 min. This technology can be applied to a wide range of pump-probe measurements in condensed matter, chemistry, and biology. 相似文献
5.
在酸性缓冲溶液中,阴离子表面活性剂十二烷基苯磺酸钠SDBS能与金鸡纳类生物碱药物体系中一对对映异构体QN和QD作用产生增强的同步光散射(synchronous light scattering,SLS)信号,本文首先利用偏振同步光散射(polarized synchronous light scattering)信号,建立了同步光散射偏振度(P)区分QN和QD这对对映异构体,同时利用同步散射光谱和双标准曲线计量分析法对2种金鸡纳类生物碱药物进行同时测定,并将该方法应用于尿样中QN和QD的同时测定,结果令人满意。 相似文献
6.
同步荧光光谱法测定水中痕量萘和菲 总被引:1,自引:0,他引:1
同步荧光法具有选择性好、灵敏度高、干扰少等特点,可用于多组分多环芳烃混合物的同时测定,本文建立了恒定波长同步荧光光谱法同时测定水中萘和菲的新方法。研究了萘和菲在不同溶剂中的荧光光谱特性,确定了同步荧光的最优波长差。当Δλ=100 nm,萘和菲激发波长(λex)分别为220.2和248.8 nm时,在0.5~25.0 μg·L-1浓度范围内,荧光强度与浓度呈现良好的线性关系,相关系数分别为0.999 5和0.999 7;萘和菲检出限均低于0.03 μg·L-1,回收率在98.0%~101.5%。该方法方便快捷,预处理简单,可用于水中萘、菲的快速测定。 相似文献
7.
A. E. Klingbeil J. B. Jeffries D. F. Davidson R. K. Hanson 《Applied physics. B, Lasers and optics》2008,93(2-3):627-638
A two-wavelength, mid-IR optical absorption diagnostic is developed for simultaneous temperature and n-dodecane vapor concentration measurements in an aerosol-laden shock tube. FTIR absorption spectra for the temperature range 323 to 773 K are used to select the two wavelengths (3409.0 and 3432.4 nm). Shock-heated mixtures of n-dodecane vapor in argon are then used to extend absorption cross section data at these wavelengths to 1322 K. The sensor is used to validate a model of the post-evaporation temperature and pressure of shock-heated fuel aerosol, which can ultimately be used for the study of the chemistry of low-vapor-pressure compounds and fuel blends. The signal-to-noise ratio of the temperature and concentration are ~20 and ~30, respectively, illustrating the sensitivity of this diagnostic. The good agreement between model and measurement provide confidence in the use of this aerosol shock tube to provide well-known thermodynamic conditions. At high temperatures, pseudo-first-order decomposition rates are extracted from time-resolved concentration measurements, and data from vapor and aerosol shocks are found to be in good agreement. Notably, the n-dodecane concentration measurements exhibit slower decomposition than predicted by models using two published reaction mechanisms, illustrating the need for further kinetic studies of this hydrocarbon. These results demonstrate the potential of multi-wavelength mid-IR laser sensors for hydrocarbon measurements in environments with time-varying temperature and concentration. 相似文献
8.
We report difference frequency generation-based wavelength converters with multiple phase-matching wavelengths that use engineered quasi-phase-matching structures in LiNbO(3) waveguides. Multiple-channel wavelength conversion is demonstrated within the 1.5-mum band and between the 1.3- and 1.5-mum bands. With simultaneous use of M pump wavelengths, these devices can also be used to perform wavelength broadcasting, in which each of N input signals is converted into M output wavelengths. 相似文献
9.
Akram-Sadat Tabatabaei-Panah Mahmood Jeddi-Tehrani Roya Ghods Mohammad-Mehdi Akhondi Nazanin Mojtabavi Ahmad-Reza Mahmoudi Ebrahim Mirzadegan Sorour Shojaeian Amir-Hassan Zarnani 《Journal of fluorescence》2013,23(2):293-302
Here we introduce novel optical properties and accurate sensitivity of Quantum dot (QD)-based detection system for tracking the breast cancer marker, HER2. QD525 was used to detect HER2 using home-made HER2-specific monoclonal antibodies in fixed and living HER2+ SKBR-3 cell line and breast cancer tissues. Additionally, we compared fluorescence intensity (FI), photostability and staining index (SI) of QD525 signals at different exposure times and two excitation wavelengths with those of the conventional organic dye, FITC. Labeling signals of QD525 in both fixed and living breast cancer cells and tissue preparations were found to be significantly higher than those of FITC at 460–495 nm excitation wavelengths. Interestingly, when excited at 330–385 nm, the superiority of QD525 was more highlighted with at least 4–5 fold higher FI and SI compared to FITC. Moreover, QDs exhibited exceptional photostability during continuous illumination of cancerous cells and tissues, while FITC signal faded very quickly. QDs can be used as sensitive reporters for in situ detection of tumor markers which in turn could be viewed as a novel approach for early detection of cancers. To take comprehensive advantage of QDs, it is necessary that their optimal excitation wavelength is employed. 相似文献
10.
Maher HM 《Journal of fluorescence》2008,18(5):909-917
Binary mixtures of naproxen and diflunisal can be resolved by using zero-crossing first derivative emission spectrofluorimetry,
first derivative constant wavelength synchronous luminescence spectrometry and first derivative constant energy synchronous
luminescence spectrometry. These methods do not require any previous separation steps. The lowest quantitation limits for
both drugs were obtained with first derivative constant wavelength synchronous luminescence spectrometry (0.002 and 0.015 μg
ml−1 for naproxen and diflunisal, respectively). The measurements were performed in 40% methanolic aqueous medium at pH 8.0 provided
by adding 0.02 M phosphate buffer solution. The proposed methods were successfully applied to the simultaneous determination
of naproxen and diflunisal in pharmaceuticals and human serum samples with high precision and accuracy. Linearity, accuracy,
precision, limits of detection, limits of quantitation, and other aspects of analytical validation are included in the text. 相似文献
11.
Simultaneous measurement of liquid water film thickness and vapor temperature using near-infrared tunable diode laser spectroscopy 总被引:1,自引:0,他引:1
A fiber-based multiplexed tunable diode-laser absorption sensor with three near-infrared distributed-feedback diode lasers
at ∼1.4 μm is used for simultaneous nonintrusive measurements of liquid water film thickness and vapor-phase temperature.
Water film thicknesses are derived from broad-band absorption determined at two fixed wavelengths while gas-phase temperature
above the film is obtained via two-line thermometry using the fast wavelength tuning with line-integrating absorption. Probing
the liquid film at two wavelengths with significantly different liquid-phase absorption cross sections allows discriminating
against additional signal losses due to surface fowling, reflection, and beam steering. The technique is demonstrated for
liquid layers of defined thicknesses and in time-resolved measurements of evaporating films. 相似文献
12.
V. T. Lebedev I. M. Dubovsky Gy. Török A. P. Serebrov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2018,12(3):426-430
Concept of spin echo spectrometer on very cold neutrons (wavelengths λ ~ 10?30 nm) to provide extra high resolution in energy transfer (ΔE ~ 10–13 eV) has been proposed. Simultaneous measurements of spin echo signals at different wavelengths will be realized using broadband spin flippers in combination with Fourier-analysis of λ-spectrum. The application of very cold neutrons should extend the spin echo time diapason radically, t ~ 10–12?10–3 s. This promises to open a set of novel scientific areas including the spectroscopy of chemical reactions and catalytic processes, conformational transitions in polymers and biological molecules, dynamic modes in carbon structures (fullerenes, nanotubes, graphenes) at scales from few nanometers to microns. Presently, the development of NSE-spectrometer on VCN becomes relevant since the project of ultra cold neutron source at WWR-M reactor (PNPI) is in progress. 相似文献
13.
The main objective of this work is to investigate the influence of high-pressure conditions on the determination of primary
particle size distributions of laser-heated soot particles using pyrometrically determined temperature decays. The method
is based on time-resolved laser-induced incandescence measurements carried out at two different wavelengths (two-colour TiRe-LII).
The LII signals are transferred into a particle ensemble averaged (effective) temperature using Planck’s thermal radiation
formula. Assuming that all particles within the size distribution possess a unique temperature at the end of the laser pulse,
the size distribution can be determined by numerically simulating the measured temperature decay. From our investigations,
for pressures up to a few bars it is obvious that this strategy can be successfully applied if standard laser pulses of nano-second
duration are used as an LII-excitation source. At higher pressures the time scales of heat conduction are decreased to such
an extent that a unique temperature for all particles within the ensemble cannot be assumed at the end of the nano-second
laser pulse. However, further investigations show that the presented two-colour TiRe-LII technique can be successfully adopted
under technical high-pressure conditions as well, if the pulse duration of the TiRe-LII-excitation source is reduced into
the pico-second range. 相似文献
14.
基于激光诱导荧光(LIF)原理和弹性散射作用于非球形粒子上形成的偏振特性,设计并研制由3个激光波长、2个接收望远镜、退偏组件和荧光光谱仪等组成的生物战剂/气溶胶Mie散射、荧光和偏振激光雷达。退偏比的水平测量结果表明:1) 退偏比表现出较强的波长依赖性;2) 多波长退偏比测量可以显著提高生物战剂的鉴别能力。退偏比的垂直测量结果表明:气溶胶在边界层内总体上维持在较低的水平,在温湿压风等气象条件和光生化条件的作用下,对流层底层空变化明显,在部分云团处,退偏振比可达0.3;气溶胶的Mie散射时空分布表明,355 nm波长的测云能力在激光出射能量相当时较532 nm强。 相似文献
15.
Peshkovsky AS Cattena CJ Cerioni LM Osán TM Forguez JG Peresson WJ Pusiol DJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,194(2):222-229
A planar nuclear quadrupole resonance (NQR) sensor has been developed. The sensor is resilient to environmental noise and is capable of simultaneous independent multi-frequency operation. The device was constructed as an open multimodal birdcage structure, in which the higher modes, generally not used in magnetic resonance, are utilized for NQR detection. These modes have smooth distributions of the amplitudes of the corresponding radiofrequency magnetic fields everywhere along the sensor’s surface. The phases of the fields, on the other hand, are cyclically shifted across the sensor’s surface. Noise signals coming from distant sources, therefore, induce equal-magnitude cyclically phase-shifted currents in different parts of the sensor. When such cyclically phase-shifted currents arrive at the mode connection point, they destructively interfere with each other and are cancelled out. NQR signals of polycrystalline or disordered substances, however, are efficiently detected by these modes because they are insensitive to the phases of the excitation/detection. No blind spots exist along the sensor’s surface. The sensor can be used for simultaneous detection of one or more substances in locations with environmental noise. 相似文献
16.
Understanding the nonlinear optical effect of novel materials plays a crucial role in the fields of photonics and optoelectronics. Herein, we theoretically and experimentally investigate the simultaneous presence of third-order locally refractive nonlinearity and thermally induced nonlocal nonlinearity saturation. We present analytical expressions for the closed-aperture Z-scan trace and the number of spatial self-phase modulation(SSPM) rings,which allows one to unambiguously and conveniently separate the contributions of local and nonlocal nonlinear refraction in the case that both effects occur simultaneously. As a test, we study both the local and thermally induced nonlocal nonlinear refraction in fullerene/toluene solution by performing continuous-wave Z-scan and SSPM measurements at two different wavelengths. This work enriches the understanding of the physical mechanism of the optical nonlinear refraction effect in solution dispersions of nanomaterials, which can be exploited for nonlinear photonic devices. 相似文献
17.
We have studied multiple regressions between the spectral aerosol extinction coefficient ε, backscatter indicatrix gπ, and light-scattering coefficients βθ at angles of θ = 1–180°, which we used to select the optimal scattering angle for determining the extinction coefficient
at the wavelengths 0.350, 0.532, and 1.060 μm. We have estimated the errors in determination of the values of ε and gπ at the given wavelengths for different atmospheric situations with different meteorological parameters. We have shown that
it is possible to use the spectral βθ values at a 33° angle to determine the reference values for ε(λ) and gπ(λ) at λ = 0.350, 0.532, and 1.060 μm in laser detection and ranging (lidar) measurements, and we give examples of recovering
the vertical profiles of ε in a slightly turbid atmosphere from the results of simultaneous multiwavelength lidar and nephelometric
measurements.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 767–772, November–December, 2007. 相似文献
18.
We present here a preliminary study concerning a multi-wavelength pyrometry method. This technique may be useful for temperature measurements on materials of unknown, selective, rapidly varying emissivity. From a (simultaneous) measurement of the thermal emission at N wavelengths, a fitting procedure leads to the simultaneous identification of the temperature and the spectral emissivity. We present first a comprehensive discussion of the various parameters influencing the accuracy of the method. Then a number of simulated experiments are calculated in order to test the efficiency of various emissivity models and to estimate the robustness of the method. It appears that measurements in the (thermal) infrared spectral range may yield satisfying temperature measurements down to T = 600 K. 相似文献
19.
Malin Jonsson Andreas Ehn Moah Christensen Marcus Aldén Joakim Bood 《Applied physics. B, Lasers and optics》2014,115(1):35-43
A method for simultaneous measurements of fluorescence lifetimes of two species along a line is described. The experimental setup is based on picosecond laser pulses from two tunable optical parametric generator/optical parametric amplifier systems together with a streak camera. With an appropriate optical time delay between the two laser pulses, whose wavelengths are tuned to excite two different species, laser-induced fluorescence can be both detected temporally and spatially resolved by the streak camera. Hence, our method enables one-dimensional imaging of fluorescence lifetimes of two species in the same streak camera recording. The concept is demonstrated for fluorescence lifetime measurements of CO and OH in a laminar methane/air flame on a Bunsen-type burner. Measurements were taken in flames with four different equivalence ratios, namely ? = 0.9, 1.0, 1.15, and 1.25. The measured one-dimensional lifetime profiles generally agree well with lifetimes calculated from quenching cross sections found in the literature and quencher concentrations predicted by the GRI 3.0 mechanism. For OH, there is a systematic deviation of approximately 30 % between calculated and measured lifetimes. It is found that this is mainly due to the adiabatic assumption regarding the flame and uncertainty in H2O quenching cross section. This emphasizes the strength of measuring the quenching rates rather than relying on models. The measurement concept might be useful for single-shot measurements of fluorescence lifetimes of several species pairs of vital importance in combustion processes, hence allowing fluorescence signals to be corrected for quenching and ultimately yield quantitative concentration profiles. 相似文献
20.
D.W. Mattison J.B. Jeffries R.R. Steeper J.E. Dec W. Hwang 《Proceedings of the Combustion Institute》2007,31(1):791-798
A wavelength-multiplexed, fiber-optic-based, line-of-sight, diode-laser absorption sensor is developed for crank-angle-resolved measurements of temperature and water concentration in a homogeneous-charge-compression-ignition (HCCI) engine. An initial demonstration of its use on two optical HCCI engines at Sandia National Laboratories is reported. The measurements encompassed both motored- and fired-engine operation for temperatures between 300 and 1700 K and pressures between 1 and 55 bar. A spectroscopic line selection process identifies the most appropriate water absorption linepair for thermometry under these conditions. Key solutions to suppress crank-angle-dependent noise in the transmitted laser signals are reported, including careful spectroscopic design and optical engineering to accommodate beam-steering, engine vibration and polarization-related interference. Data obtained through this sensor can provide critical engine characteristics such as combustion efficiency, peak combustion temperature, and autoignition temperature. The flexibility of the wavelength-multiplexed architecture allows the straightforward addition of other wavelengths to potentially enable the simultaneous measurement of other important engine parameters such as temperature non-uniformity, and fuel, CO, and CO2 concentrations. 相似文献