Laser Induced Fluorescence

Top PDF Laser Induced Fluorescence:

Laser-Induced Fluorescence of Wet Porous Silicon as Laser-Induced Fluorescence of H3O+

Laser-Induced Fluorescence of Wet Porous Silicon as Laser-Induced Fluorescence of H3O+

Abstract: Typically, the production of porous silicon is an electrochemical etching of monocrystalline silicon wafers, which are connected to the anode, in ethanol-aqueous HF solutions. In the process of etching, it turns out porous silicon, which is saturated with water, which is rich in protonated molecules H 3 O + , formed as a result of a number of well-known physicochemical processes. At the same time, the presence of molecules of such protonated water in the composition of freshly prepared porous silicon is usually ignored. At the same time, both the ability of protonated water to fluoresce under the action of laser radiation in the UV range, and the possible contribution of such fluorescence to the total fluorescence of porous silicon induced by a UV laser is ignored. Since such ignoring seems to be incorrect, the possible contribution of laser fluorescence of water enriched with its protonated molecules to the laser fluorescence of moistened porous silicon is discussed here. Since this may be important for the correct interpretation of the results obtained when studying the spectra of laser-induced fluorescence of porous silicon moistened with aqueous solutions, in particular – with aqueous solutions of biological substances, the unique properties of such water are also demonstrated. Thus, the exceptional penetrating ability of positively charged water is visualized, due to which it is able to transfer from the hydrated shells of biopolymers to porous silicon and enhance its laser- induced fluorescence. It also demonstrates the exceptional ability of positively charged water to evaporate; which makes it possible to explain the rapid disappearance of the fluorescence of porous silicon, which is observed during its drying.
Show more

5 Read more

Laser induced fluorescence measurements of spheromak plasmas

Laser induced fluorescence measurements of spheromak plasmas

4.7 Discussion The laser induced fluorescence experimental technique developed on the earlier coaxial spheromak gun has been successfully adapted for use with the new coplanar sphe- romak device. Independent sets of measurements performed on Ar II plasmas produced with the same experimental control settings yield virtually identical calculated ion param- eters, suggesting reasonable plasma reproducibility. Measurements have been performed with the probing laser oriented either perpendicular to or parallel to the spheromak’s axis of symmetry; the ability to make measurements in either orientation is significant, as it suggests one possible course for future expansion of the experiment. In addition, param- eter estimates derived from data provided by both passive spectroscopy and visible light photography are in reasonable agreement with the ion densities and propagation rates calculated from the LIF measurements performed in this work.
Show more

136 Read more

Argon ion laser-induced fluorescence with diode lasers

Argon ion laser-induced fluorescence with diode lasers

Diode lasers have been used for ion temperature measurements in ArII plasmas by finding new laser-induced fluorescence ~ LIF ! schemes suited to the present range of available wavelengths. The new LIF schemes require excitation at 664, 669, and 689 nm, all near industry-standard wavelengths. Conventional LIF measurements performed by dye lasers in ArII use 611.66 nm in vacuum, shorter than any commercially available red diode laser line, and depend on the population of the 3d 8 2 G 9/2 metastable state. The metastable state density of the conventional LIF scheme was found to be larger than the populations of the other metastable states by an order of magnitude or less. A master oscillator power amplifier diode laser was used both in a Littman–Metcalf cavity and as an optical amplifier for a low power diode laser which was in a Littman–Metcalf cavity. Both systems provided intensity of up to 500 mW, continuously tunable over 10 nm centered at 666 nm, and were used to obtain high resolution ion velocity distribution functions. © 1998 American Institute of Physics. @ S0034-6748 ~ 98 ! 04201-4 #
Show more

6 Read more

Laser induced fluorescence study on the growth of maize plants

Laser induced fluorescence study on the growth of maize plants

Remote sensing techniques are widely used these days to study plants. In remote sensing applications, laser- induced fluorescence (LIF) is a powerful technique, which can be used for early remote sensing of stress conditions in plants [4,5]. LIF is an active sensing tech- nique capable of capturing immediate and specific indi- cations of changes in plant physiology and metabolism as they relate to the concentration and photosynthetic activity of the plant pigment. There are several advan- tages in the use of pulsed UV lasers as excitation sources.

7 Read more

Laser induced fluorescence in Nd3+ : LaCl3. I. - Hyperfine structures

Laser induced fluorescence in Nd3+ : LaCl3. I. - Hyperfine structures

Abstract. 2014 The laser induced fluorescence line-narrowing technique has been used to obtain high-resolution spectra of isotopically enriched 143Nd3+ and 145Nd3+ ions in a LaCl3 host. Nuclear magnetic dipole interactions have been investigated for the 4I9/2 ~ 2H11/2 and 4I9/2 ~ 4G5/2 transi- tions in two-level and three-level systems.

6 Read more

Simple Laser-Induced Fluorescence Setup to Explore Molecular Spectroscopy. Abstract

Simple Laser-Induced Fluorescence Setup to Explore Molecular Spectroscopy. Abstract

Abstract We will demonstrate a relatively simple, affordable and highly visual experiment to explore molecular spectroscopy by measuring the laser-induced fluorescence (LIF) spectrum of the iodine molecules at room temperature. Iodine is a uniquely suited molecule for LIF measurements since it conveniently absorbs about 20,000 lines in the 490- to 650-nm visible region of the spectrum and serves excellent example of displaying discrete vibrational bands at moderate resolution and rotational structure at high resolution.

12 Read more

INVESTIGATION OF NATURAL CONVECTION IN CUBICAL ENCLOSURE USING LASER INDUCED FLUORESCENCE

INVESTIGATION OF NATURAL CONVECTION IN CUBICAL ENCLOSURE USING LASER INDUCED FLUORESCENCE

Temperature measurements are extremely important and they are used in many technical and engineering processes, including the analysis of natural convection. In contrast to the commonly used thermocouples and Pt100 temperature sensors, which allow point temperature measurements, laser induced fluorescence tech- nique (LIF) allows the imaging of temperature fields throughout the area. An ob- vious disadvantage of thermocouples and Pt100 sensors is the possibility that the probes can affect the fluid flow, changing its structure. This problem does not ap- pear in LIF measurements and better accuracy of temperature mapping is ob- tained. This work focuses on describing one-color LIF technique (using one fluo- rescent dye) in theoretical and practical terms. The experimental set-up is de- scribed, as well as a number of operations required to get the temperature field of the whole domain. The results of the natural convection process analysis in the configuration of one side wall heated and the opposite one cooled, with the use of laser induced fluorescence technique are presented.
Show more

8 Read more

Two-photon laser-induced fluorescence in sodium-doped composite propellant flame

Two-photon laser-induced fluorescence in sodium-doped composite propellant flame

signal is typically detected by photosensitive elements. Concentrations and temperatures can be determined based on the LIF signals. Planar laser-induced fluorescence is the two- dimensional variant of this technique. Sodium LIF has been investigated in a variety of combustion and aerodynamic environments due to the easy accessibility of the sodium D line transition and its extremely high absorption cross section. Although sodium one-photon LIF has been successfully used to measure the velocity 88 , temperature 89 , and concentration 21 of seeded gaseous jets, they often require corrections in high optical density environments due to the resonant excitation and collection of the fluorescence signal. As discussed in Chapter 2 for the one-photon absorption LIF in sodium, the easiest transition to access (D-line) has a resonant detection wavelength which is the same as the excitation wavelength. For atomic systems with high density, this leads to the re-absorption and re-fluorescence of LIF photons before reaching the edge of the flame and the detector. The first sub-section will describe some initial characterization with the one-photon LIF system.
Show more

92 Read more

A study of heat transfer in forced convective drying with the application of laser induced fluorescence thermometry

A study of heat transfer in forced convective drying with the application of laser induced fluorescence thermometry

technique was also tested using an emerging fluorescent tracer material, anisole, for which there are only a few studies to date. The relationship between toluene fluorescence intensity and temperature was validated over a temperature scale significantly smaller than in previous studies. Despite some inac- curacy in inferring temperature measurements, it was found that laser-induced fluorescence thermometry can be applied successfully in low temperature scales and used as a tool for studying heat transfer distribution across solid geometries. Using the single colour technique, the error of temperature measurement was found to range between 2 ◦ C and 10 ◦ C for temper- atures of 20 ◦ C and 95 ◦ C, respectively. This is comparable to the error ranges of previous studies. A novel method for increasing the temperature-sensitivity by time-resolving the fluorescence signal has also been proposed. This led to a 50% increase in the sensitivity of the temperature measurements. This technique has not been performed to date and is particularly useful for low temperature scales where the sensitivity between fluorescence intensity and temperature is limited.
Show more

227 Read more

Laser Induced Fluorescence Studies of Blood Plasma and Tumor Tissue of Men with Prostate Tumors

Laser Induced Fluorescence Studies of Blood Plasma and Tumor Tissue of Men with Prostate Tumors

Objectives: Fluorescence spectroscopy which can be used for optical tissue diagnosis of tumor pa- thology deserves special interest. The purpose of the work was to study blood plasma and tumor tissue of men with different forms of prostate tumors by using laser induced fluorescence. Blood plasma and tumor tissue of the patients with benign hyperplasia of the prostate (BHP), BHP with inflammation, BHP with high grade PIN (BHP with HGPIN) and adenocarcinoma of prostate (CaP) have been studied. Results: In case of blood plasma fluorescence, intensity of the plasma proteins corresponding peak (340 - 360 nm) was increasing in the following manner: control group → BHP
Show more

11 Read more

Field Observations with Laser-Induced Fluorescence Transient (LIFT) Method in Barley and Sugar Beet

Field Observations with Laser-Induced Fluorescence Transient (LIFT) Method in Barley and Sugar Beet

Received: 13 February 2014; in revised form: 18 April 2014 / Accepted: 12 May 2014 / Published: 22 May 2014 Abstract: The laser-induced fluorescence transient (LIFT) method is a non-invasive remote sensing technique for measurement of photosynthetic performance of plants under laboratory and field conditions. We report here a long-term comparative study to monitor the performance of different cultivars of barley and sugar beet during the growth season of these crops. The LIFT measurements provided useful results about photosynthetic light use efficiency on selected leaves in the canopy of the studied crops. The different canopy architectures, with different optical properties, influenced the LIFT measurements.
Show more

11 Read more

Using planar laser-induced fluorescence to study the phase transformations of two-component liquid and suspension droplets

Using planar laser-induced fluorescence to study the phase transformations of two-component liquid and suspension droplets

Original Manuscript Submitted: 3/31/2019; Final Draft Received: 4/1/2019 Using the planar laser-induced fluorescence (PLIF), we performed experiments to determine evaporation dynamics of homogeneous and heterogeneous droplets of liquids, conditions of their boiling, and explosive breakup. For the 1–2 mm water droplets, the distribution of highly non-homogeneous and non-steady temperature field was detected by high- speed cross-correlation video recording and the Tema Automotive software. We identified highly nonlinear dependences of evaporation rate on heating temperature and time as well as water droplet size. For the two-component liquids and water-based suspensions of graphite, we revealed unsteady temperature fields and established mechanisms and regimes of the explosive breakup of the heterogeneous droplets when heated. The regimes differ in the number and dimensions of the emerging gas–liquid fragments as well as the durations of the main stages. The three regimes of warming-up and evaporation of the heterogeneous droplets have been obtained. The explosive breakup of droplets enables provision for the secondary atomization of the liquid with the emergence of an aerosol cloud. The surface area of the liquid increases several-fold. The temperature variations at the water/solid or water/flammable component interfaces were determined corresponding to each boiling and breakup regime. Using the PLIF, we studied reasons and mechanism of the explosive breakup of water droplets with single large carbonaceous inclusions when heated.
Show more

13 Read more

Mixed Micellar Electrokinetic Chromatographic Analysis of Colistin, Polypeptide Antibiotic, Using Laser Induced Fluorescence Detection

Mixed Micellar Electrokinetic Chromatographic Analysis of Colistin, Polypeptide Antibiotic, Using Laser Induced Fluorescence Detection

Keywords: Capillary Electrophoresis; Laser-Induced Fluorescence; Urine Direct Injection; Mixed Micelles; Derivatization; Colistin; Polypeptide Antibiotic; MEKC 1. Introduction Colistin is a cationic polypeptide and is one of the po- lymyxin antibiotics known as polymyxin E, produced by Bacillus colistinus. It has a significant in vitro activity against some multiresistant Gram-negative pathogens, including Pseudomonas aeruginosa (P. aeruginosa). Till now there are limited studies on its clinical use, pharma- cokinetics and pharmacodynamics. The two commercially available forms of colistin are colistin sulphate, chiefly used topically, and sodium colistin methanesulphonate, used parenterally. Both forms may be given via inhala- tion. Early experience showed it to be an effective an- timicrobial agent for the treatment of septicaemias, wound infections, urinary tract infections and respiratory system
Show more

9 Read more

An Investigation of the Krypton Laser-Induced Fluorescence Spectral Lineshape for Composition-Independent Thermometry Applied to Combustion Environments.

An Investigation of the Krypton Laser-Induced Fluorescence Spectral Lineshape for Composition-Independent Thermometry Applied to Combustion Environments.

ZELENAK, DOMINIC CHARLES. An Investigation of the Krypton Laser-Induced Fluorescence Spectral Lineshape for Composition-Independent Thermometry Applied to Combustion Environments. (Under the direction of Dr. Venkat Narayanaswamy). Temperature is an important thermochemical property in combustion that holds the key to uncovering several combustion phenomena. Laser diagnostics have become popular tools for non- disruptive thermochemical measurements in reacting flows, owing to their relative simplicity in implementation and their ability to provide multi-dimensional, temporal, and multi-variable measurements. In a practical combustion environment, the local composition is typically unknown, which hinders the effectiveness of many traditional non-intrusive thermometry techniques. This study aims to offset this limitation by developing laser-based thermometry techniques that do not require prior knowledge of the local composition. Recent developments of Kr LIF have encouraged its extension to composition-independent thermometry and pressure measurements in gaseous combustion, as seeded krypton gas offers several significant advantages over other seeded or in situ species extensively featured in previous works.
Show more

200 Read more

Investigation of potential interferences in the detection of atmospheric ROx radicals by laser-induced fluorescence under dark conditions

Investigation of potential interferences in the detection of atmospheric ROx radicals by laser-induced fluorescence under dark conditions

Laser-induced fluorescence (LIF) is a widely used tech- nique for the direct detection of atmospheric OH radicals. In general, laser-wavelength modulation is applied to distin- guish the OH fluorescence from non-resonant, laser-excited background signals. The concept cannot, however, discrimi- nate between fluorescence from ambient OH, which is sam- pled into a low-pressure cell, and OH that may be artificially produced inside the detection cell. In recent field studies, sig- nificant artifacts from spurious OH have been reported for two LIF OH instruments (Mao et al., 2012; Novelli et al., 2014a), when the sampled air contained alkenes and ozone. The artifacts were discovered by applying a chemical titra- tion scheme that destroys ambient OH before entering the low-pressure detection cell. In this operational mode, the re-
Show more

17 Read more

Density measurement of OH radicals in non-thermal plasmas by laser induced fluorescence and time-resolved absorption spectroscopy

Density measurement of OH radicals in non-thermal plasmas by laser induced fluorescence and time-resolved absorption spectroscopy

46 CHAPTER 3. LASER INDUCED FLUORESCENCE RET collisions were considered also in [68] and [67]. The six-level model of [67] was also used in [69]. In this model the two ro-vibronic N and N 0 states involved in the absorption process are connected by total RET collision rates to two additional “lumped” states that include the whole remaining rotational manifold of the (X, υ = 0) and (A, υ = 1) vibro- electronic states. Given that RET rates, although somewhat uncertain, are very high, it was shown in [66] that the model outcomes are substantially independent of the exact values of RET rates, provided these are sufficiently larger than the absorption rate. Then the model can be simplified by dropping the two equations for the lumped states and setting the N and N 0 states always at Boltzmann equilibrium with the gas temperature. This is equivalent to saying that RET are so fast that both X and A rotational manifolds achieve equilibrium with the gas temperature at any time during the laser pulse. The validity of this four-level model was empirically tested with a 250 µm diameter laser beam with energy up to 9 µJ.
Show more

153 Read more

MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel

MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel

Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 time- correlated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transi- tional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified. © 2010 Optical Society of America
Show more

11 Read more

Mixing of the Immiscible Liquids in the Entrance Region of a T-Type Chamber Using Laser Induced Fluorescence (LIF) Method

Mixing of the Immiscible Liquids in the Entrance Region of a T-Type Chamber Using Laser Induced Fluorescence (LIF) Method

advanced technique with thymol blue, a indicator used as a dye that fades with mixing. Thymol blue in stagnant tap water takes about half an hour to fade, but rapidly fades with agitation. Wood et al. [10], captured images of mixing reactors flow seeded with polystyrene particles with an average diameter of 100 μm. The shutter speeds on the camera were varied so that the particles present in the fluid appeared as streaks in the images. More recently, flow laser induced fluorescence visualization techniques, 𝜇-LIF by Hoffmann et al. [11], and PLIF by Sultan et al. [12], have also been used to study different flow regimes and mixing quality in impingement mixing in micro mixers with rectangular cross-sections. Laser-induced fluorescence (LIF) is a non- intrusive technique for measuring scalar concentrations in fluid flows [14]. The most common application of LIF in fluid flows is two-dimensional planar laser induced fluorescence (PLIF). [14] In PLIF, a laser is used to excite a fluorescent species within the flow. Typically, the tracer is an organic fluorescent dye such as fluorescein or rhodamine. The dye absorbs a portion of the excitation energy and spontaneously re-emits a portion of the absorbed energy as fluorescence. The fluorescence is measured optically and used to infer the local concentration of the dye.
Show more

11 Read more

Accurate identification of nitrogen fertilizer application of paddy rice using laser-induced fluorescence combined with support vector machine

Accurate identification of nitrogen fertilizer application of paddy rice using laser-induced fluorescence combined with support vector machine

To identify accurately the doses of nitrogen (N) fertilizer and improve the photosynthetic efficiency of paddy rice, laser induced fluorescence (LIF) technique combined with the support vector machine (SVM) and principal com- ponent analysis (PCA) is proposed in this paper. The LIF technology, in which the ultraviolet light (355 nm) is ap- plied as an excitation light source, is employed to measure fluorescence spectra of paddy rice. These fluorescence spectra demonstrate that the fluorescence spectral characteristics of paddy rice leaves with different doses of N fertilizer have distinct differences from each other. Then, PCA and SVM are implemented to extract the features of fluorescence spectra and to recognize different doses of N fertilizer, respectively. The overall recognition accuracy can reach 95%. The results show that the LIF technology combined with PCA and SVM is a convenient, rapid, and sensitive diagnostic method for detecting N levels of paddy rice. Thus, it will also be convenient for farmers to man- age accurately their fertilization strategies.
Show more

6 Read more

optical Pumping With Laser-Induced Fluorescence

optical Pumping With Laser-Induced Fluorescence

The phoiocurreni generated by the probe laser’s photodiode was detected across 200 kn, and amplified by 200 before being displayed on the oscilloscope: (a) pump laser blocked, 20 mV/cm;[r]

11 Read more

Show all 10000 documents...