An examination of the first laser-induced fluorescence measurements of ion-acoustic wave reflection is presented in this dissertation. The experiment is performed in a multipole cylinindrical chamber using singly-ionized argon (ArII) plasma produced by a means of a hot cathode. Ion-acoustic waves are launched from a mesh antenna and reflected/absorbed by a biased, solid boundary (electrode). A kinetic analysis of wave reflection is carried out through LIF's ability of resolving ion phase-space. A comparison between Langmuir probe and LIF diagnostics is presented, with complementary Electric-field probe measurements.

This thesis demonstrates a measurement of a plasma fluctuation velocity-space cross-correlation matrix using laser induced fluorescence. The plasma fluctuation eigenmode structure on the ion velocity distribution function can be empirically determined through singular value decomposition from this measurement. This decomposition also gives the relative strengths of the modes as a function of frequency. Symmetry properties of the matrix quantify systematic error. The relation between the eigenmodes and plasma kinetic fluctuation modes is explored. A generalized wave admittance is calculated for these eigenmodes. Since the measurement is a localized technique, it may be applied to plasmas in which a single point measurement is possible, multipoint measurements may be difficult, and a velocity sensitive measurement technique is available.

This study proposed a novel design of the passive micromixer which employed several quadrilateral shaped blocks in the micro channel to enhance mixing. Both numerical and experimental investigations have been carry out. Commercial software CFD-ACE was used to simulate the flows. The simulation results showed great agreement with the measured results, implying that Navier¡VStokes¡¦ equations still effectively governs the micro-scope flows in this scale. It is effective to enhance mixing efficiency over wide flow rate ranges. Mixing performance was characterized by Laser-induced-fluorescence system (LIF system) to quantity the concentration distribution in the micro channel . In addition, Microscopic flow visualization was also setup to visualize the flow field in the micro mixer. Micro-particle image velocimetry (Micro-PIV) was used to measure the flow fields in microchannel filled with deionized water (DI water) . The system utilizes an epifluorescent microscope, 3.3 £gm diameter seed particles, and an high speed CCD camera to record particle-image fields. The vector fields are analyzed using a double-frame cross-correlation algorithm. The stochastic influence of Brownian motion plays a significant role in the accuracy of instantaneous velocity measurements.

No description available.

Transient molecules are of great importance due to their critical role as intermediates in the semiconductor industry, in upper atmosphere reactions, and in astrochemistry. In the present work, reactive intermediates were produced in the laboratory by applying an electric discharge through a suitable precursor gas mixture and studied by means of their laser-induced fluorescence and emission spectra. The band systems of and have been studied in detail. The energy levels of both isotopologues were fitted with a Renner-Teller model, and the isotope relations have been used to test the validity of the derived parameters. The A2Πu - X 2Πg electronic transition of jet-cooled has been detected and shown to originate from the Ω=3/2 spin-orbit component of v=0 of the ground state. For the first time, the 0-0 band has been identified and vibrational assignments have been made. Our ab initio studies show that the extensive observed perturbations are due to spin-orbit interaction between A2Πu(3/2) and B2Δu(3/2) states. The experimental data were fitted to an effective Hamiltonian and yielded the spin-orbit coupling term =240 cm-1. LIF and emission spectra of the transition of N2O+ have been recorded. Both spin-orbit components of the band were studied at high resolution and rotationally analyzed, providing precise molecular constants. Emission spectra provided extensive data on the ground state vibrational levels which were fitted to a Renner-Teller model including spin-orbit and Fermi resonance terms. The previously unknown electronic spectrum of the H2PO radical has been identified. Ab initio predictions were used to aid in the analysis of the data. The band system is assigned as the electronic transition. The excited state molecular structure was determined by rotational analysis of high resolution LIF spectra. The band systems of the HBCl and DBCl free radicals have been studied in detail. This electron promotion involves a linear-bent transition between the two Renner-Teller components of what would be a 2Π electronic state at linearity. Ab initio potential energy surface calculations were used to help in assigning the LIF spectra which involve transitions from the ground state zero-point level to high vibrational levels of the excited state.

Radicals are interesting to study because of importance in so many processes such as semiconductor growth or stellar evolution. Laser induced fluorescence (LIF) and wavelength resolved emission spectra of jet cooled HPS, HAsO, AsD2, H2PS, and F2BO have been measured using the pulsed discharge jet technique. Several bands in the à 1A′′ − X̃ 1A′ transition of HPS were observed and assigned with the help of ab initio calculations. The ab initio geometries showed that HPS does not follow Walsh’s predictions for the angle change upon electronic excitation; Walsh predicts an increase in HPS upon excitation while a decrease is calculated. Ab initio Walsh-style orbital angular correlation diagrams for both electronic states show a change in correlation for some orbitals upon electronic excitation, an effect that Walsh did not predict. The à 1A′′ − X̃ 1A′ transitions were measured in HAsO and DAsO for the first time. A molecular geometry was derived for each electronic state from experimental rotational constants. The experimental geometries prove that HAsO also violates Walsh’s rules for the same reason shown in HPS. The à 2A1 – X̃ 2B1 electronic transition of AsD2 and AsHD were measured. Vibrational levels observed in emission were fit to a local mode vibrational Hamiltonian. Using the previously reported rotational constants for AsH2 and those determined for AsD2 in this work, an improved estimate of the excited state geometry was obtained. The discovery of the B̃ 2A′ − X̃ 2A′ band system of H2PS is the first report of this molecule. Both D2PS and HDPS were also observed. Ab initio calculations helped assign the transition. H2PS is one of the few tetra-atomic or larger molecules that violates Kasha’s empirical rule due to the large separation between the B̃ and à states. Finally, laser induced fluorescence spectra of the F2BO radical was observed for the first time. Previous work showed two band systems with only a tentative assignment. The measured LIF spectra confirm the identity of the two band systems as the B̃ 2A1 – X̃ 2B2 and the B̃ 2A1 – à 2B1 transitions showing F2BO also violates Kasha’s rule.

Concern for the nonphysiologic energy required to actuate medical devices utilizing “smart material” properties of shape memory polymer (SMP) compels a rigorous investigation into the flow and temperature fields surrounding a thermally activated catheter device. Multiple analyses include the theoretical approaches of exact analytical solutions and finite difference modeling combined with the experimental techniques of particle image velocimetry (PIV) and laser-induced fluorescence (LIF). The attained velocities and temperatures related to the convective heat transfer impact the potential for blood or tissue damage caused by intravascular heating. The clinical scenario involving a catheter device receiving heat within an artery is modeled in its simplest form as a cylindrical metal cap on the tip of a hollow glass rod placed inside of a long straight tube of constant cross-sectional area. Using a working fluid with properties comparable to blood, flow rates and energy input is then varied to determine their effects on velocity fields and temperature gradients. Analytical solutions for both the straight tube and concentric annulus demonstrate the two velocity distributions involved, as flow moves past the gap between the catheter and artery wall and then converges downstream to the Poiseuille solution for steady pipe flow of an incompressible fluid. To solve for the transition between the velocity profiles, computational fluid dynamics software simulates a finite volume model identical to the experimental setup used for intravascular heating experiments. PIV and LIF, both experimental techniques making use of similar hardware, determine velocity fields and temperature distributions, respectively, by imaging fluid seeding agents and their particular interaction with the light sheet. The velocity and temperature fields obtained experimentally are matched with the analytical and finite volume analysis through fluid properties, flow rates, and heating rates. Velocities determined during device heating show a small increase in local velocity, due to temperature dependent viscosity effects. When the device is centered in the model, flow patterns constrain the heat flow near the center axis and away from the channel walls. Increasing flow rate consequently decreases temperature rise, as the heat is carried more quickly downstream and away from the heat source. Using multiple analyses, fluid velocity and temperature distributions are first theorized with analytical and finite element methods and then validated through experimental imaging in a physical model.

abstract: This thesis describes the studies for two groups of molecules in the gas-phase: (a) copper monofluoride (CuF) and copper hydroxide (CuOH); (b) thorium monoxide (ThO) and tungsten carbide (WC). Copper-containing molecules (Group a) are selected to investigate the ionic bonding in transition metal-containing molecules because they have a relatively simple electronic state distribution due to the nearly filled 3d-orbital. ThO and WC (Group b) are in support of particle physics for the determination of electron electric dipole moment (eEDM), de, the existence of which indicates new physics beyond the Standard Model. The determination of the tiny eEDM requires large electric fields applied to the electron. The 3(Delta)1 states for heavy polar molecules were proposed [E. R. Meyer, J. L. Bohn, and M. P. Deskevich, Phys. Rev. A 73, 062108 (2006)] to determine de with the following attractive features: (1) large electric dipole moments; (2) large internal electric fields, Eeff, experienced by valence electrons; (3) nearly degenerate omega-doublets; (4) extremely small magnetic dipole moments. The H3(Delta)1 state for ThO and the X3(Delta)1 state for WC are both good candidates. Spectroscopic parameters (i.e. molecular electric and magnetic dipole moments, omega-doubling parameters, etc) are required for the 3(Delta)1 states of ThO and WC. High resolution optical spectra (linewidth ~50 MHz) of CuF, CuOH, ThO and WC were recorded field-free and in the presence of a static electric field (or magnetic field) using laser ablation source/supersonic expansion and laser induced fluorescence (LIF) detection. The spectra were modeled by a zero-field effective Hamiltonian operator and a Stark (or Zeeman) Hamiltonian operator with various molecular parameters. The determined molecular parameters are compared to theoretical predictions. The small omega-doubling parameter was well determined using the pump/probe microwave optical double resonance (PPMODR) technique with a much higher resolution (linewidth ~60 kHz) than optical spectroscopy. In addition to the above mentioned studies of the two groups of molecules, a resonance enhanced multi-photon ionization (REMPI) combined with a time-of-flight mass spectrometer (TOFMS) has been developed to identify the molecules responsible for observed LIF signals. The operation of this spectrometer has been tested by recording the mass spectrum of Ti/O2 and the REMPI spectrum for TiO using a two-color excitation scheme. / Dissertation/Thesis / Ph.D. Chemistry 2012

Métodos convencionais para o estudo da combustão são geralmente métodos intrusivos (por exemplo, uso de termopares para medida da temperatura da chama), que acarretam distúrbios na queima (efeitos térmicos, catalíticos ou aerodinâmicos). As técnicas de diagnóstico utilizando lasers, além de serem não intrusivas, possuem uma alta resolução temporal e espacial que permite mapear a zona de combustão e identificar em cada ponto da chama os diversos estados em que se formam os radicais transientes. Neste trabalho foi estabelecida a técnica de fluorescência induzida por laser, LIF - \"Laser Induced Fluorescence\" - do radical OH para a determinação da temperatura em chamas de etanol/Oxigênio/ar. Esta técnica é bastante utilizada em outros países, mas no Brasil é inédita. Para o início dos estudos, foi construído um queimador para queima de combustíveis líquidos, produzindo chamas pré-misturadas. Foram testados esquemas de emissão de LIF (309,5 nm-311,5 nm) e de excitação de LIF, esta em duas regiões de absorção do radical OH A2\'sigma\'\'seta\'X2 \'pi\' (0,0) (303 nm e 309 nm) e A2\'sigma\'seta\'X2\'pi\'(1,0) (278 nm - 280 nm). Os melhores resultados foram obtidos pelo método de excitação de LIF na região das transições S21(1) - S21(13) da banda A2\'sigma\'X2\'pi\' (1,0), utilizando o gráfico de Boltzmann. Foram feitas medições em chamas de etanol em várias posições ao longo do seu eixo longitudinal, acima do queimador, e para vazões com razões de equivalência =1,0 = 1,4 e = 0,82. Os resultados foram comparados com os obtidos pela técnica da linha reversa utilizando um sal de sódio e apresentaram dados concordantes dentro dos erros experimentais. As temperaturas obtidas ao longo de 55 mm da chama de etanol variaram de 2008 K +- 40 K a 2246 K +- 90 K para razão de equivalência = 0,82; de 2198 K +- 65 K a 2295 K +- 127 K para razão de equivalência = 1,0 e de 1905 K +- 64 K a 2238 K +- 155 K para razão de equivalência = 1,4. Chamas de GLP também foram estudadas em 3 posições ao longo de 15 mm da chama com razões de equivalência, 1,0; 1,5 e 0,87. As temperaturas variaram de 2423 K +- 102 K a 2622 K +- 106 K para razão de equivalência = 0,87; de 2441 K +- 110 K a 2631 K +- 100 K para razão de equivalência = 1,0 e de 2403 K +- 109 K a 2605 K +- 124 K para razão de equivalência = 1,5. O presente estudo mostrou que a técnica de LIF é adequada para o mapeamento da temperatura de chamas, tanto de combustíveis gasosos quanto líquidos. As temperaturas obtidas apresentaram um desvio experimental menor do que 8 %. / Conventional methods for the study of combustion are usually intrusive methods (for example, the use of thermocouples to measure flame temperatures), which might disturb the burning process (thermal, catalytic or aerodynamic effects). The diagnostics techniques using lasers, in addition to being non-intrusive, have high temporal and spatial resolution. They allow the “mapping” of in which the combustion zone and the identification, at each point of the flame, the various states in which the transient radicals are formed. In this work, the technique of Laser Induced Fluorescence (LIF) was used. This technique is based on the spectral emission from the OH radical species for the determination of the temperature in ethanol/oxigênio/air flames. This technique is largely employed in other countries, but in Brazil it has not been employed to study combustion processes. In the first step of our studies, a liquid fuel burner was constructed, producing premixed flames. Experimental setups for LIF emission (309,5 nm - 311,5 nm) and excitation, in two regions of the OH radical absorption spectrum A-X (0,0) (303 nm and 309 nm) and A-X (1,0) (278 nm - 280 nm) were tested. The best results were obtained by excitation in the region of the transitions S21(1) - S21(13) of the A-X (1,0) band, using the plot of Boltzmann. Measurements in ethanol flames at different positions along the burner vertical axis were obtained, and for flowsrates with equivalence ratios 1.0; 1.4 and 0.82. The results were compared with those obtained with the sodium line-reversal technique and agree within the experimental error values. The temperature values measured throughout a 55 mm distance above the burner in the ethanol flame varied from 2008 K ± 40 K to 2246 K ± 90 K for equivalence ratio 0.82; from 2198 K ± 65 K to 2295 K ± 127 K for equivalence ratio 1.0 and from 1905 64 K ± to 2238 K ± 155 K for equivalence ratio 1.4. Mixture of propane/butane flames were also studied in three positions throughout a 15 mm distance above the burner for equivalence ratios,equivalence ratio 1.0 equivalence ratio = 1.5 and equivalence ratio 0.87. The temperatures measured varied from 2423 K ± 102 K to 2622 K ± 106 K for equivalence ratio 0.87; from 2441 K ± 110 K to 2631 K ± 100 K for equivalence ratio 1.0 and from 2403 K ±109 K to 2605 K ±124 K for equivalence ratio 1.5. The present study shows that the LIF technique is suitable for “mapping” flame temperatures of gaseous as well as liquid. The temperatures measured showed experimental deviations lower than 8 %.

La métrologie non-intrusive est une composante essentielle de la recherche expérimentale en mécanique des fluides. La connaissance instantanée des champs de vitesse et de température apportent des informations essentielles à la compréhension des phénomènes instationnaires aérothermiques. Toutefois, si les mesures de vitesses sont aisément réalisées, l’obtention de champs de température s’avère plus complexe. L’une des voies étudiées pour y parvenir estla Fluorescence Plane Induite par LASER, ou PLIF. Son principe repose sur l’acquisition de signaux lumineux de fluorescence, dépendants de la température, consécutifs à l’excitation du milieu par un faisceau LASER intense. En particulier, la PLIF acétone à deux longueurs d’onde emploie l’acétone comme traceur fluorescent et deux LASER comme source d’excitation pour s’affranchir de la dépendance en concentration en acétone. Toutefois, selon la longueur d’onde,l’énergie LASER ou la gamme de température explorée, la PLIF-2λ peut s’avérer difficile à mettre en oeuvre du fait d’un manque de sensibilité, lié à un signal de fluorescence trop faible.Dès lors, plusieurs étapes correctives visant à améliorer le rapport signal-sur-bruit peuvent être mises en oeuvre. Le présent travail s’intéresse ainsi à déterminer la pertinence de cette méthode métrologique dans la qualification aérothermique d’un écoulement de convection mixte autour d’un cylindre chauffé, en couplant la PLIF-2λ à la Vélocimétrie par Imagerie de Particules(PIV). Le montage expérimental est détaillé, ainsi que les processus correctifs et l’étalonnage mis en place pour la PLIF. Les résultats expérimentaux sur le cylindre chauffé sont ensuite présentés et comparés aux travaux de la littérature, puis un modèle de la fluorescence et des caméras employées est élaboré pour permettre d’estimer la précision atteignable en pratique selon la longueur d’onde, l’énergie LASER, la concentration et les caméras, et ainsi rendre possible la présélection des équipements nécessaires aux travaux futurs. / Non-intrusive metrology is essential in experimental fluid mechanics experiments. In particular, simultaneous acquisition of instantaneous velocity and temperature fields offers valuable insights in instationnary aerothermal behaviours. However, if instantaneous velocity fields can be acquired quite easily using the Particles Image Velocimetry technic (PIV), instantaneous temperature fields are much more complex to obtain. Plannar Laser Induced Fluorescence (PLIF) is one of the technics allowing such a measurement. The emitted LASER light induces excitation of acetone molecules, the tracer in the studied air flow. Then, the fluorescence following de-excitation, which is temperature-dependant, is recorded. In particular, 2 λ-PLIF uses dual wavelength LASER excitation to remove acetone concentration dependency in the measurement. Yet, depending of the wavelengths, the LASER energy or the temperature range investigated, using 2 λ-PLIF can be difficult due to a very low temperature sensitivity and very dim fluorescence. To solve those issues and improve signal-to-noise ratio, acquired images can be corrected according to different parameters in an interative process. Present work is dedicated to evaluate efficiency of corrected 2 λ-PLIF applied to the study of a mixed convection flow around a heated cylinder in the 20-300 C temperature range. The goal is to obtain aerothermal qualification of the flow thanks to simultaneous 2 λ-PLIF and PIV. In the present work, experimental bench is detailled as well as the calibrating and correcting process of the 2 λ-PLIF. Then, experimental results are discussed and confronted to results from litterature. Finally, a model of the fluorescence and camera-generated noise is discussed and used to generate simulated fluroescence images and determine the impact of all parameters (wavelengths, LASER energy, acetone concentration and camera intensification gain) on the measurement precision and thus enable adequate choice of equipments for next experiments.