Dissertations / Theses on the topic 'Raman'
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Ali, Momenpour. "Raman Biosensors." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36468.
Full textKunarajah, Enoch Arumaishanth. "Distributed Raman amplifiers." Thesis, University of Essex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399979.
Full textNash, J. "Time resolved Raman scattering in liquid crystals using a Raman microprobe." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356443.
Full textTanaka, Tomoyoshi. "Resonance raman and surface enhanced raman studies of hemeproteins and model compounds." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/27678.
Full textDelhaye, Caroline. "Spectroscopie Raman et microfluidique : application à la diffusion Raman exaltée de surface." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13927/document.
Full textThis thesis focuses on the development of a microfluidic platform coupled with confocal Raman microscopy, used in excitation conditions of Raman scattering (Surface enhanced Raman scattering, SERS) in order to gain in the detection sensitivity of molecular species flowing in channels of micrometer dimensions. This work aims to demonstrate the feasibility of coupling Raman microscopy / microfluidics for the in situ and local characterization of species and reactions taking place in the fluid flowing in microchannels. We used a T-shaped microchannel, made by soft lithography, in which gold or silver nanoparticles injected at constant speed, in one of the two branches of the channel and a solution of pyridine or pefloxacin in the other one. The laminar flow and the stationarity of the process allowed us to map the mixing zone and highlight the enhancement of the Raman signal of pyridine and pefloxacin, due to the metallic nanoparticles, in the interdiffusion zone. The recording of the both absorption band of the silver nanoparticles (plasmon band) and the Raman signal of pefloxacin, flowing in microchannel, allowed us to establish a link between the shape of the metallic nanostructure, and more precisely the silver nanoparticle aggregation state, and the enhancement of the Raman signal of pefloxacin observed. We then changed the channel geometry to introduce an electrolyte solution (NaCl and NaNO3) and locally modify the surface charge of the colloids. We have put in evidence that the change of the silver nanoparticle aggregation state, induced by the controlled addition of electrolyte solutions, could amplify the SERS signal of pefloxacin and thus optimizing the detection in microfluidics. At last, we established second a approach that consists in the metallic structuring of microchannel walls. This has shown that the surface chemical functionalization through organosilanes (APTES) allowed the pasting of the channel with silver nanoparticles, thus amplifying the Raman signal of the species flowing within the same microchannel
Cazayous, Maximilien. "Interférences Raman et Nanostructures." Phd thesis, Université Paul Sabatier - Toulouse III, 2002. http://tel.archives-ouvertes.fr/tel-00001850.
Full textWiley, James Hugh. "Raman spectra of celluloses." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5748.
Full textHagen, Johannes. "Spektral beherrschter Raman-Faserlaser /." Aachen : Shaker, 2008. http://d-nb.info/988549115/04.
Full textGrantier, David Raymond. "Chemically induced raman scattering." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30321.
Full textLi, Yun-Thai. "Tip-enhanced Raman spectroscopy." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609992.
Full textPatil, Raj. "Deep UV Raman Spectroscopy." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/613378.
Full textNathaniel, Todd. "Spatial heterodyne Raman spectroscopy." Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/810642/.
Full textCéreyon, Arnaud. "Amplification Raman et nanostructures." Lyon 1, 2008. http://www.theses.fr/2008LYO10133.
Full textMaher, Robert Christopher. "Surface enhanced Raman scattering." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/7843.
Full textPetrak, Benjamin James. "Microcavity Enhanced Raman Scattering." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6354.
Full textCalizo, Irene Gonzales. "Raman nanometrology of graphene." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359892.
Full textIncludes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 8, 2010). Includes bibliographical references (p. 59-64). Also issued in print.
Bergqvist, Saga. "Raman spectroscopy in neurosurgery." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-78665.
Full textHjärntumörer kan drabba människor i alla åldrar, medelåldern för människor som lever med en hjärntumör är 60 år, men det är ett tillstånd som även drabbar barn och unga i stor utsträckning. Hjärntumörer är den näst vanligaste cancerformen hos barn och är även den främsta orsaken till cancerrelaterad död i den åldergruppen. För att minimera skadorna på hjärnan är det viktigt att en tumör kan lokaliseras och tas bort så tidigt som möjligt. De metoder som används idag bygger framför allt på biopsi, där en del av tumören tas bort och undersöks av en histopatalog. Det är en process som tar lång tid och även påverkas av den mänskliga faktorn, det finns därmed ett behov av en metod som kan avändas \textit{in situ} som ger ett resultat som inte påverkas av den mänskliga faktorn. En metod som har visat lovande resultat är fotosensibilisering med 5-Aminolevulinsyra (5-ALA). Desvärre har den metoden bara visat sig fungera bra för högmaligna tumörer hos vuxna. Som ett komplement till fotosensibilisering har Ramanspektroskopi visat lovande resultat i tidigare genomförda studier. Det här arbetet genomfördes för att undersöka användningen av Ramanspektroskopi som ett verktyg för diagnostisering av hjärntumörer. Som grund användes två tidigare genomförda studier där de undersökte Ramanband från biologiska markörer i hjärnvävnad som ändras i cancerogen vävnad. De undersökte även hur den biokemiska sammansättningen av hjärnvävnaden ändrades genom att jämföra intensiteten av olika Ramanband. Ett mätsystem för Ramanspektroskopi designades och byggdes upp på Luleå Tekniska Universitet där det även testades på vävnad från kött (fläsk och biff). Därefter transporterades mätsystemet till Linköpings Universitet för att genomföra mätningar på sex olika vävnadsprov från fem hjärntumörer av olika malignitet. Baserat på en preliminär histopatalogisk bedömning var en av tumörerna högmalignt och de fyra andra tumörerna var antingen lågmalignta eller benigna. Två av proverna som undersöktes kom från den högmalignta tumören som även var fotosensibilierad med 5-Aminolevulinsyra, varav ett av proverna var belyst med blått ljus innan de Ramanspektroskopiska mätningarna genomfördes. Innan resultatet från Ramanspektroskopiska mätningarna analyserades behandlades datan med konventionella metoder i MatLab. I de resulterade spektrumen gick det att se tydliga Ramanband associerade med hjärnvävnad. Det gick även att se Ramanband associerade med 5-ALA i de två prover som var fotosensibiliserade och i det provet som var belyst med blått ljus innan de spektroskopiska mätningarna gjordes gick det även att se tydliga Ramanband associerade med hjärnvävnad. När resultatet analyserades gick det även att se spektra associerat med reducerat Neuroglobin (NGB) i ett av proverna. Sammansättningen av NGB är också någonting som ändras i cancerogen vävnad och skulle därför också kunna användas som en bilogisk markör för hjärntumörer i framtida studier. När resultaten från den här studien jämfördes med de tidigare studierna indikerade den ena studien att två av vävnadsproverna kom från en högmalignt tumör och att de resterande fyra från lågmaligna eller benigna tumörer, vilket stämmer överens med den preliminära diagnosticeringen av tumörerna. När resultatet istället jämfördes med den andra studien stämde inte resultatet lika bra med den preliminära diagnosticeringen av tumörerna. Metoden presenterad av Zhou m.fl. indikerade att alla tumörer kom från lågmaligna eller benigna tumörer. Slutsaten av det här arbetet är att Ramanspektroskopi skulle kunna användas som en metod för diagnosticering av hjärntumörer. Metoden skulle även fungera bra som ett komplement till fotosensibilisering med 5-ALA eftersom att det var möjligt att se Ramanband associerade med hjärnvävnad när vävnaden hade belysts med blått ljus.
Cancado, Luiz Gustavo de Oliveira Lopes. "Raman spectroscopy of nanographites." Universidade Federal de Minas Gerais, 2006. http://hdl.handle.net/1843/IACO-6W8NYM.
Full textResumo: No presente trabalho investigamos alguns efeitos físicos que acontecem na estrutura e evolução estelar. Focalizamos nossa atenção em estrelas de baixa massa na pré-sequência principal. Incluímos alguns efeitos físicos no código de estrutura e evolução estelar ATON2.3, escrito pelo Dr. Ítalo Mazzitelli (1989) e posteriormente modificado pelo Dr. Luiz Themystokliz Sanctos Mendes (1999b) para adicionar os efeitos de rotação e redistribuição interna de momento angular. Com o objetivo de economizar tempo computacional, introduzimos o mecanismo de parada de controle (checkpoint), que permite iniciar uma dada execução em um estágio de evolução intermideário, desde que os passos iniciais tenham sido devidamente registrados. Essas modificações foram feitas juntamente com um controle completo de variáveis não inicializadas, precisão e reestruturação do programa, visando futuramente paralelizar o código. Introduzimos efeitos combinados de rotação e forças de maré na configuração de equilíbrio das estrelas. Estes efeitos perturbadores, contidos na função potencial total, desviam a forma da estrela da aproximação esfericamente simétrica. Usamos o método de Kippenhahn & Thomas (1970), posteriormente aperfeiçoado por Enda & Sofia (1976). À função potencial obtida por estes autores, adicionamos termosrelacionados à forças de maré e àqueles relacionados à parte não simétrica do potencial gravitacional devido à distorção que tais forças causam na figura da estrela. Seguindo esta aproximação, corrigimos as equações constitutivas a fim de obter uma configuração estrutural de uma estrela distorcida. Cálculos de constantes de estrutura interna e raios de giração foram incluídos no código. Várias trilhas evolutivas foram geradas com os novos modelos, incluindo as quantidades mencionadas acima. Os novos modelos foram testados através de dados observacionais das dimensões absolutas, taxa de movimento apsidal e abundância de lítio das componentes do sistema binário eclipsante EK Cephei. No presente trabalho, também apresentamos estimativas teóricas do convective turnover time, Tc e Números de Rossby, Ro, para estrelas com massas semelhantes à massa solar, com rotação e na pré-sequência principal. Ro está relacionado com a força magnética na teoria do dínamo e, pelo menos para estrelas na seqüência principal, observa-se uma correlação entre rotação e atividade estelar. Incluímos também a possibilidade de utilizar modelos de atmosferas não cinza, com o objetivo de seguir a evolução estelar de estrelas de baixa massa desde estágiosbem iniciais, caracterizados por baixa gravidade. Adotamos os modelos NextGen e ATLAS9 de atmosferas estelares. Usando os nossos novos modelos não-cinza, geramos vários conjuntos de trilhas evolutivas, partindo da pré-sequência principal. Tais trilhas foram usadas para investigar algumas propriedades físicas e rotacionais de estrelas jovens na Nebulosa de Orion. Comparações entre resultados teóricos e dados observacionais, permitiram-nos obter informações sobre esta classe de objetos, principalmente no que diz respeito à distribuição inicial de momento angular. A interpretação dos dados depende fortemente das considerações físicas feitas no modelos, sendo a eficiência da convecção a mais importante. Nossa análise indica que um segundo parâmentro é necessário para descrever a convecção na pré-sequência principal. Tal parâmetro está possivelmente relacionado ao efeito estrutural de um campo magnético gerado por efeito dínamo.
SPEISER, EUGEN. "Raman spectroscopy on nanostructures." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/566.
Full textNajjar, Samar. "Couplage AFM/Raman et spectroscopie Raman exaltée par effet de pointe de nanostructures." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00869044.
Full textGühlke, Marina. "Oberflächenverstärkte Hyper-Raman-Streuung (SEHRS) und oberflächenverstärkte Raman-Streuung (SERS) für analytische Anwendungen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17570.
Full textHyper-Raman scattering follows different symmetry selection rules than Raman scattering and, as a non-linear two-photon process, profits even more than Raman scattering from enhanced electromagnetic fields at the surface of plasmonic nanostructures. Surface-enhanced hyper-Raman scattering (SEHRS) could thus gain practical importance for spectroscopy. The combination of SEHRS and surface-enhanced Raman scattering (SERS) offers complementary structural information. Specifically, due to the localization of the enhancement to the close proximity of the nanostructures, this information can be utilized for the characterization of the interaction between molecules and metal surfaces. The aim of this work was to increase the understanding of the SEHRS effect and to assess its applicability to answer analytical questions. For that purpose, SEHRS experiments with excitation at 1064 nm and SERS experiments with excitation at the same wavelength, as well as with excitation at 532 nm - to detect SEHRS and SERS in the same spectral region - were conducted. As an example for non-resonant excitation, pH-dependent SEHRS and SERS spectra of para-mercaptobenzoic acid were examined. Based on these spectra, the interaction of different silver nanostructures with the molecules was characterized. beta-Carotene was used to study the influence of resonance enhancement by the excitation of a molecular electronic transition during SEHRS experiments. By the thiol-functionalization of carotene, a more intense interaction with the silver surface was achieved, which enables to obtain not only resonant SEHRS and SERS but also non-resonant SERS spectra of carotene. Hyperspectral SEHRS imaging in combination with microspectroscopy was demonstrated by analyzing the distribution of different dyes on structured plasmonic surfaces.
Guo, Yu. "RAMAN SPECTROSCOPY OF GLASSESWITH HIGH AND BROAD RAMAN GAIN IN THE BOSON PEAK REGION." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4275.
Full textPh.D.
Department of Physics
Sciences
Physics
Ulrichs, Edzard. "Raman-Spektroskopie an niedrigdimensionalen Elektronensystemen." [S.l. : s.n.], 2000. http://www.sub.uni-hamburg.de/disse/123/DISS.pdf.
Full textMohammed, Abdelsalam. "Theoretical Studies of Raman Scattering." Doctoral thesis, KTH, Teoretisk kemi (stängd 20110512), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28332.
Full textQC 20110112
Souza, Marcelo Abreu de. "Espectroscopia Raman de altos explosivos." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-09022007-150540/.
Full textSelected high explosives were characterized by Raman and Infrared spectroscopies and the effect of temperature was followed in-situ by Raman spectroscopy. TNT, HMX, RDX, PETN (commercial products) and TATP belong to distinct chemical families (except HMX and RDX) and their response to heating was evaluated. The samples were first characterized by FT-IR, FT-IR/ATR and Raman with excitation in the visible (632.8 nm) and in the NIR (1064 nm) aiming at the detection of sampling effects in the obtained spectra, specifically phase transitions and degradation. ATR and FT-Raman were the techniques of choice to provide the spectra for band assignment, which was assisted by theoretical simulations (DFT). Each sample was heated up to a temperature well below its melting point, in order to avoid thermal decomposition. The bands most affected by temperature were taken as the routes for energy relaxation in explosives. The obtained results lead to the conclusion that PETN decomposes through the rupture of the C-ONO2 bond, whereas in HMX and RDX the N-N bond is broken. TNT spectra indicates that the NO2 and C-N vibrations are the most sensitive to temperature and TATP sublimated at 70°C and no bands were affected by temperature. The results are agreement with the literature or theoretical simulations.
McGoverin, Cushla Maree, and n/a. "Raman spectroscopy of complex mixtures." University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081103.112612.
Full textLiu, Xiaohua. "Resonance raman studies of hemoproteins." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/27170.
Full textCastillo, Carolina Graciela. "Biological applications of raman spectroscopy." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30414.
Full textLewis, Steffan A. E. "Fibre Raman amplifiers for telecommunications." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288385.
Full textParr, Andrea Ann. "Raman microscopy studies of polysilicon." Thesis, Northumbria University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324468.
Full textThomas, Chapman. "Autoresonance in Stimulated Raman Scattering." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00674111.
Full textO'Grady, Noelle Antoinette. "Raman spectroscopy of fluorescent samples." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246542.
Full textRussell, K. T. "Raman spectroscopic studies of asbestos." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355239.
Full textZugic, Minjas. "Raman spectra of clathrate hydrates." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271176.
Full textNarula, Rohit. "Resonant Raman scattering in graphene." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/118567.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 131-144).
In this thesis we encounter the formulation of a rigorous theory of resonant Raman scattering in graphene, the calculation of the so-obtained Raman matrix element K2f,1o for the 2D Raman mode with the full inclusion of the matrix elements and a physically appealing bridge between theory and experiment by eschewing the problematic ascription of graphene with a finite thickness. Finally, we elucidate an experimental study of the Raman D and G modes of graphene and highly-defected pencil graphite over the visible range of laser radiation. Marking a departure from the usual practice for light scattering in semiconductors of including only the dynamics of the electrons and holes separately, we show via fourth-order quantum mechanical perturbation theory using a Fock state basis that for resonant Raman scattering in graphene the processes to leading order are those that involve the simultaneous action of the electrons and holes. Such processes are indeed an order of magnitude stronger than those prevalent in the literature under the double resonance [1, 2, 3] moniker. We translate our perturbation theoretic analysis into simple rules for constructing Feynman diagrams for processes to leading order and we thereby enumerate the 2D and D modes. Using expressions for the terms to leading order obtained from our theoretical treatment we proceed to evaluate the Raman matrix element [4] for the Raman 2D mode by using state-of-the-art electronic [5] and iTO phonon dispersions [6] fit to ab initio GW calculations. For the first time in the literature we include the variation of the light-matter and electron-phonon interaction matrix elements calculated via an ab initio density functional theory (DFT) calculation under the local density approximation (LDA) for the electronic wavefunctions. Our results for the peak structure, position and intensity dependence are in excellent agreement with experiments [7, 8, 9, 10]. Strikingly, our results show that depending on the combination of the input (polarizer) and output (analyzer) polarization of the laser radiation, very different regions of the phonon dispersion are accessed. This has a direct impact on the dominant electronic transitions according to the pseudo-momentum conservation condition satisfied by the scattering of an electron by a phonon ki = kf + q. Using sample substitution [11] we deconvolve the highly wavelength dependent response of the spectrometer from the Raman spectra of graphene suspended on an SiO2 - Si substrate and graphite for the D and G modes in the visible range. We derive a model that considers graphene suspended on an arbitrary stratified medium while sidestepping its problematic ascription as an object of finite thickness and calculate the absolute Raman response of graphene (and graphite) via its explicitly frequency independent Raman matrix element [K'2f10]2 vs. laser frequency. For both graphene and graphite the [K'2f10]2 per graphene layer vs. laser frequency rises rapidly for the G mode and less so for the D mode over the visible range. We find a dispersion of the D mode position with laser frequency for both graphene and graphite of 41 cm-YeV and 35 cm-YeV respectively, in good agreement with Narula and Reich 131 assuming constant matrix elements, the observed intensity follows the joint density states of the electronic bands of graphene. Finally, we show the sensitivity of our calculation to the variation in thickness of the underlying SiO2 layer for graphene.
by Rohit Narula.
Ph. D.
Danilovic, Borka. "Étude Raman des supraconducteurs organiques." Mémoire, Université de Sherbrooke, 1999. http://savoirs.usherbrooke.ca/handle/11143/4459.
Full textRodrigues, Pedro Augusto Matos. "Espalhamento Raman por semicondutores mesoscópicos." [s.n.], 1988. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277696.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nós desenvolvemos um modelo para o espectro Raman de semicondutores microcristalinos. Neste modelo o confinamento dos fonons tem dois efeitos: a) produz uma relaxação da lei de conservação do momento cristalino; b) limita as vibrações óticas permitidas àquelas que satisfaçam a condição de onda estacionária. Estas modificações em relação a um cristal macroscópico resultam em um espectro Raman composto de vários picos que é claramente distinto daquele de um cristal macroscópico mesmo no caso em que o tamanho dos microcristais não é constante em toda a amostra. Nossos resultados são utilizados para caracterizar amostras de CdSe microcristalino obtido por deposição química
Abstract: We developed a model for the Raman spectrum of small semiconductors crystallites. In this model phonon confinement has two effects: a) it produces a relaxation of the k conservation rule. b) it limits the amount of allowed optical vibrations to those which obey the stationary wave condition. These modifications with respect to macroscopic crystal result in a Raman spectrum containing several peaks which is clearly distinguished from that of bulk materials even in the case where the crystallite size is not constant throughout the sample. Our results are used to characterize microcrystalline samples of CdSe obtained by chemical deposition
Mestrado
Física
Mestre em Física
Moreira, Alessandro Ferreira Lisboa. "Espalhamento Raman em perovskitas duplas." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277693.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nesse trabalho foram realizados estudos em duas famílias de compostos de perovskitas duplas Ba2FeReO6 e S r2UO6 (B'= Co, Ni) por espectroscopia Raman e difração de raios-X com luz síncrotron. No primeiro composto há uma transição de uma estrutura cúbica Fm3m paramagnética para uma tetragonal I4/mmm ferrimagnética abaixo de TC~305 K. O mecanismo de acoplamento magnético neste material ainda permanece uma incógnita. Dois grupos de medidas de espalhamento Raman foram realizados em regiões distintas da amostra à base de FeRe. Foi verificado que o fônon associado às vibrações de estiramento dos oxigênios nos octaedros sofre um desvio na freqüência em relação ao comportamento convencional abaixo de TC nos dois grupos de medidas. Isso pode ser associado a dois possíveis mecanismos: acoplamento spin-fônon gigante e acoplamento órbita-spin-fônon. Na segunda família de compostos contendo urânio, os compostos estudados apresentam uma estrutura cristalina monoclínica com grupo espacial P 21/n e um ordenamento antiferromagnético abaixo de TN~21 K para B" = Ni e TN~10 K para B" = Co. A partir dos espectros Raman desses compostos observa-se que a área integrada do modo de estiramento do oxigênio sofre um decréscimo anômalo sob aquecimento até T*~300 K. Além disso, este modo sofre um endurecimento anômalo de ~1 cm -1 sob aquecimento até T*. Para verificar a hipótese de que T* poderia estar associada a uma transição estrutural nesta família, medidas de difração de raios-X de pó com luz síncrotron foram realizadas no LNLS. A análise estrutural de ambos os compostos não mostraram nenhum grau observável de desordem de antisítios entre B' e U e tampouco uma transição de fase ou comportamento anômalo dos parâmetros de rede foi encontrada em torno de T*. Portanto, as anomalias encontradas em espectroscopia Raman nestes materiais são de origem eletrônica
Abstract: In this work, studies on two families of double perovskite compounds Ba2FeReO6and Sr2B'U O6(B' = Ni, Co) were carried out by Raman spectroscopy and synchrotron X-ray diffraction. In the first compound, a transition from a cubic Fm3m paramagnetic to a tetragonal ferromagnetic structure takes place below TC ~305 K. The magnetic coupling mechanism in this material remains unknown. Two groups of Raman scattering measurements were performed in distinct regions of the FeRe-based sample. It was verified that the phonon associated to stretching vibrations of oxygen octahedra shows a frequency shift with respect to the conventional behavior below TC, in both groups of measurements. This may be associated with two possible mechanisms: giant spin-phonon coupling and orbit-spin-phonon coupling. In the second family of compounds with uranium, the studied compounds present a monoclinic crystal structure with space group P21/n and an antiferromagnetic ordering below TN~21 K for B'' = Ni and TN ~10 K for B'' = Co. From the Raman spectra of these compounds, an anomalous decrease of the integrated area of the oxygen stretching mode was observed upon heating up to T*~300 K. Also, this mode shows an anomalous hardening of ~1 cm -1 under heating up to T*. In order to verify the hypothesis that T* could be associated to a structural transition in this family, powder x-ray diffraction measurements with synchrotron light were perfomed at LNLS. The structural analysis of both compounds did not show any observable degree of antisite disorder between B' and U, and no phase transition or anomalous behavior of lattice parameters was found close to T*. Therefore, the anomalies found by Raman spectroscopy in these materials are electronic in origin
Mestrado
Física da Matéria Condensada
Mestre em Física
Ribeiro, Henrique Bücker. "Espectroscopia raman em materiais bidimensionais." Universidade Presbiteriana Mackenzie, 2017. http://tede.mackenzie.br/jspui/handle/tede/3485.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fundação de Amparo a Pesquisa do Estado de São Paulo
Fundo Mackenzie de Pesquisa
In this thesis, the properties of four kinds of layered materials were investigated: twisted bilayer graphene, black phosphorus, germanium selenide (GeSe) and germanium sulfide (GeS) (group IV monochalcogenides) by means of Raman spectroscopy. The Raman spectrum of different twisted bilayer graphene samples rotated by different angles ranging from 0 to 30 was measured using three lasers with wavelengths of 488 nm, 532 nm, and 633 nm. The electronic structure of the investigated samples was mapped and the energy in which the resonances take place were attributed to the presence of van Hove singularities that are related to the size of Moiré cell. Angular dependence measurements of the Raman spectrum on black phosphorus (BP) samples were also performed and it was demonstrated that the angular dependence of the Raman band intensities presents an unusual behavior. In order to explain such behavior, one must consider the complex nature of the Raman tensors. Furthermore, the atomic structure and phonon behavior in the vicinity of the BP sample edges were also studied using polarized Raman spectroscopy and the experimental results were explained by using density functional theory calculations. Polarized Raman spectra showed the appearance of some modes at the edges of the samples prohibited by symmetry selection rules. Theoretical simulations confirm that this symmetry breaking originates from an atomic rearrangement at the edges of the crystal. A similar behavior was also observed for GeS and GeSe samples and the appearance of Raman modes of the edges was attributed to the reorganization of the atoms of the crystal edges, since their crystal structure are similar to that of BP crystals.
Nesta tese investigamos as propriedades de quatro tipos de materiais bidimensionais: grafeno bicamada rodado(empilhamento de duas camadas com diferentes ângulos de rotação entre camadas), fósforo negro, seleneto de germânio e sulfeto de germânio (monocalcogenetos do grupo IV) por meio de espectroscopia Raman. O espectro Raman de diferentes amostras de grafeno rodado com diferentes ângulos de rotação entre as camadas, variando entre 0_ a 30_ foram medidos utilizando lasers com comprimentos de onda de 488nm, 532nm e 633nm. As estruturas eletrônicas das amostras investigadas foram mapeadas e a energia em que as ressonâncias acontecem foram atribuídas às singularidades de van Hove que estão relacionadas com o tamanho da célula de Moiré obtida pela rotação de uma camada em relação a outra. Medidas de dependência angular do espectro Raman em amostras de fósforo negro(BP) foram também realizadas e foi demonstrado que a dependência angular dos espectros Raman apresenta um comportamento não usual. Para explicar tal comportamento foi mostrado que deve-se sempre considerar a natureza complexa dos elementos do tensor Raman. A estrutura atômica e comportamento de fônons nas proximidades da borda de amostra de BP foi também estudada experimentalmente usando espectroscopia Raman polarizada e explicada teoricamente usando cálculos baseados na teoria do funcional da densidade. Os espectros Raman polarizados mostraram o aparecimento de modos nas bordas das amostras, normalmente proibidos por regras de seleção de simetria da fase bulk. As simulações teóricas confirmaram que a quebra de simetria se origina de uma reorganização atômica nas bordas do cristal. Esse mesmo fenômeno foi também observado em amostras de GeS e GeSe que apresentam uma estrutura cristalina similar à de cristais de BP.
Bonhomme, Frédéric. "Spectroélectrochimie par microspectroscopie Raman confocale." Bordeaux 1, 2000. http://www.theses.fr/2000BOR10526.
Full textLi, Zheng Ph D. Massachusetts Institute of Technology. "Computational Raman imaging and thermography." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130673.
Full textCataloged from the official PDF of thesis.
Includes bibliographical references (pages 185-201).
Thermography tools that perform accurate temperature measurements with nanoscale resolution are highly desired in our modern society. Although researchers have put extensive efforts in developing nanoscale thermography for more than three decades and a significant amount of achievements have been made in this field, the mainstream thermography tools have not fully met the requirements from the industry and the academia. In this thesis, we present our home-built Raman microscope for Raman imaging and thermography. The performance of this instrument is enhanced by computational approaches. The body of the thesis will be divided into three parts. First, the instrumentation of our setup are introduced. Second, we present the results of Raman imaging with computational super-resolution techniques. Third, this instrument is used as a thermography tool to map the temperature profile of a nanowire device. These results provide insights in combining advanced instrumentation and computational methods in Raman imaging and Raman thermography for the applications in modern nano-technology.
by Zheng Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
Nemeth, Amanda. "Raman Signature of Molecular Charging." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1609258734249143.
Full textRaghunathan, Varun. "Raman-based silicon photonic devices." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1481677321&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Full textDanilovic, Borka. "Étude Raman des supraconducteurs organiques." Sherbrooke : Université de Sherbrooke, 2000.
Find full textBoozer, Allen David Kimble H. Jeff. "Raman transitions in cavity QED /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05272005-160246.
Full textThomson, Grant. "Forensic applications of Raman spectroscopy." Thesis, University of Leeds, 2002. http://etheses.whiterose.ac.uk/395/.
Full textCalmes, Lonnie Kirkland. "Solid-state Raman image amplification." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288920.
Full textCastellani, Carlos Eduardo Schmidt. "Amplificadores Raman em fibras microestruturadas." Universidade Federal do Espírito Santo, 2009. http://repositorio.ufes.br/handle/10/6211.
Full textCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The development of microstructured fibers, also known as photonic crystal fibers (PCF), which has happened principally during the last decade, has raised new possibilities on the field of optics and telecommunications due to its capability of presenting some constructive parameters with non conventional values. In the context of optical communications, more precisely on the construction of optical amplifiers, these photonic crystal fibers also have brought some new interesting possibilities. Due to its capability of at the same time presents very high negative dispersion and high non linearity, it allows for example, the construction of Raman amplifiers with high gains that also compensate dispersion with reduced fiber lengths. The conventional silica-based fibers need tens of kilometers of fiber length to accomplish the same task. Taking advantage of that situation, the main purpose of this dissertation is exactly the project and the study of multi-pump Raman amplifiers operating as discrete devices providing gain and compensating dispersion over the entire C band, using a PCF. In order to project such amplifiers, an optimization technique made through an exhaustive search based on an analytical solution method for the signal propagation is proposed. The analysis of these amplifiers is made via computational simulations that are done with numerical and also analytical models, by means of the verification of the gain, ripple, optical signal to noise ratio (OSNR), and eye penalty parameters. Their performance is also evaluated by comparing the performance of a Raman amplifier operating with a conventional dispersion compensating fiber (DCF).
O desenvolvimento de fibras óticas microestruturadas, também conhecidas como fibras de cristal fotônico - PCF (Photonic Crystal Fibers), que se deu principalmente na última década, trouxe novas possibilidades no campo da ótica e das telecomunicações devido à sua capacidade de apresentar alguns parâmetros construtivos com valores não convencionais. No contexto de comunicações óticas, mais precisamente na construção de amplificadores ópticos, essas fibras de cristal fotônico também trouxeram algumas novas possibilidades interessantes. As PCFs são capazes de ao mesmo tempo apresentar dispersão muito negativa e alta não-linearidade, permitindo, por exemplo, a construção de amplificadores Raman com altos ganhos e que ainda compensem a dispersão utilizando apenas poucos quilômetros de fibra. As fibras de sílica convencionais necessitam de dezenas de quilômetros para realizar a mesma tarefa. Aproveitando-se dessa situação, o foco principal desta dissertação é justamente o projeto e o estudo do funcionamento de amplificadores Raman multibombeio, que operem como dispositivos discretos fornecendo ganho e compensando a dispersão em toda a banda C, através da utilização de uma PCF. Para projetar tais amplificadores é proposta uma técnica de otimização feita através de uma busca exaustiva baseada em um método de solução analítico de propagação de sinais. A análise desses amplificadores é realizada através de simulações computacionais feitas com modelos numéricos e também analíticos, por meio da verificação dos parâmetros de ganho, ripple, relação sinal ruído ótica OSNR (Optical Signal-to-Noise Ratio), e penalidade de diagrama de olho. Seu desempenho é também avaliado em termos de uma comparação com o desempenho de um amplificador Raman funcionando com uma fibra compensadora de dispersão DCF (Dispersion Compensating Fiber) convencional.
CASTELLANI, C. E. S. "Amplificadores Raman em Fibras Microestruturadas." Universidade Federal do Espírito Santo, 2009. http://repositorio.ufes.br/handle/10/9596.
Full textO presente projeto de pesquisa visa estudar o comportamento de sistemas ópticos WDM de altas taxas operando com amplificadores Raman em fibras microestruturadas. Esse estudo será feito através da análise de parâmetros como Ganho, ripple, penalidade de diagrama de olho e relação sinal-ruído ótica (OSNR optical signal to noise ratio), que serão obtidos com a utilização de modelos computacionais, analíticos e numéricos, já desenvolvidos pelo Laboratório de telecomunicações da UFES (Labtel). Pretende-se fazer a otimização de configurações com múltiplos bombeios para que seja verificada a viabilidade ou não da utilização desse tipo de fibra para amplificação Raman em sistemas de longa distância, bem como a sua utilização como fibra compensadora de dispersão.
Weigel, Alexander. "Femtosecond stimulated resonance Raman spectroscopy." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16302.
Full textFemtosecond stimulated Raman spectroscopy is a powerful tool that allows to study the structural relaxation of an excited chromophore directly in time. In this work a tunable Raman spectrometer with 10 cm-1 spectral and 50-100 fs temporal resolution was developed, and the technique was advanced towards applications to flavin-based proteins. With this device the influence of resonance conditions on the transient Raman spectrum is characterized. Excited-state dynamics is first investigated for the model photoswitch stilbene, starting from both the cis and the trans isomers. Decay, spectral shift, and narrowing of individual bands provide insight into the vibrational relaxation of the excited chromophore. Wavepacket motion and anharmonic coupling is seen as oscillations. Isomerization is followed to the ground state for the "parent" cyanine 1,1''-diethyl-2,2''-pyrido cyanine iodide. From a global analysis, Raman spectra for the Franck-Condon region, the intermediately populated hot ground state, and the isomerization products are obtained. As a basis for experiments on flavoproteins, the excited-state properties of the pure flavin chromophore are studied in solution. Transient absorption and fluorescence experiments suggest an influence of dynamic polar solvation on the electronic properties of the excited state. Raman spectra from the flavin excited state are recorded and the vibrational bands assigned. Population depletion by the Raman pulse is identified as a potential artefact, but the effect is also used to mark wavepacket motion in the excited state. The photoreceptor mutants BlrB-L66F and Slr1694-Y8F are studied by transient absorption; signaling state formation and flavin reduction by a semiconserved tryptophan are seen, respectively. The application of femtosecond Raman spectroscopy to biological samples is demonstrated in a first experiment on glucose oxidase.