<p>The accurate description of ground and electronic excited states is an important and challenging topic in quantum chemistry. The pairing matrix fluctuation, as a counterpart of the density fluctuation, is applied to this topic. From the pairing matrix fluctuation, the exact electron correlation energy as well as two electron addition/removal energies can be extracted. Therefore, both ground state and excited states energies can be obtained and they are in principle exact with a complete knowledge of the pairing matrix fluctuation. In practice, considering the exact pairing matrix fluctuation is unknown, we adopt its simple approximation --- the particle-particle random phase approximation (pp-RPA) --- for ground and excited states calculations. The algorithms for accelerating the pp-RPA calculation, including spin separation, spin adaptation, as well as an iterative Davidson method, are developed. For ground states correlation descriptions, the results obtained from pp-RPA are usually comparable to and can be more accurate than those from traditional particle-hole random phase approximation (ph-RPA). For excited states, the pp-RPA is able to describe double, Rydberg, and charge transfer excitations, which are challenging for conventional time-dependent density functional theory (TDDFT). Although the pp-RPA intrinsically cannot describe those excitations excited from the orbitals below the highest occupied molecular orbital (HOMO), its performances on those single excitations that can be captured are comparable to TDDFT. The pp-RPA for excitation calculation is further applied to challenging diradical problems and is used to unveil the nature of the ground and electronic excited states of higher acenes. The pp-RPA and the corresponding Tamm-Dancoff approximation (pp-TDA) are also applied to conical intersections, an important concept in nonadiabatic dynamics. Their good description of the double-cone feature of conical intersections is in sharp contrast to the failure of TDDFT. All in all, the pairing matrix fluctuation opens up new channel of thinking for quantum chemistry, and the pp-RPA is a promising method in describing ground and electronic excited states.</p> / Dissertation

La photo-isomérisation par ouverture de cycle du benzopyrane a été étudiée à l'aide de la méthode MCTDH (Multi-Configuration Time-Dependent Hartree). Nous avons introduit différentes stratégies pour contrôler la conversion du benzopyrane en mérocyanine à l'aide d'impulsions laser. Nous avons utilisé un modèle pour le potentiel électronique à six dimensions développé dans le cadre d'un travail antérieur. Le modèle repose sur une généralisation des Hamiltoniens modèles standards pour les couplages vibroniques et utilise les six coordonnées les plus importantes pour le processus. Le principal objectif est de fournir des stratégies de contrôle qui pourront être utilisées par les expérimentateurs par la suite. Plus précisément, nous avons proposé: (i) une technique de type pompe-sonde pour contrôler la photostabilité, (ii) une stratégie en deux étape avec une préexcitation vibrationnel du système,(iii) une stratégie reposant sur un contrôle par effet Stark induit par un laser non-résonant. / The ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection,has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use asix-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of thevibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of strategies that could help experimentalists tocontrol the photoreactivity vs. photostability ratio (selectivity). In this work we present:(i) a pump-dump technique used tocontrol the photostability, (ii) a two-step strategy to enhance the reactivity of the system: first, a pure vibrational excitation inthe electronic ground state that prepares the system and, second, an ultraviolet excitation that brings the system to the firstadiabatic electronic state; (iii) finally the effect of a non-resonant pulse (Stark effect) on the dynamics.

O objetivo do presente estudo foi determinar a área alargada posterior ao retratamento do canal radicular com instrumentos de níquel-titânio em imagens de tomografia computadorizada de feixe cônico. Sessenta raízes mesiais de molares inferiores foram selecionadas e submetidas a tomografia computadorizada de feixe cônico(TCFC) em 4 períodos de: antes do preparo (T1), após o preparo (T2), após o retratamento (T3) e após a complementação do retratamento (T4). Após a TCFC inicial (T1), os dentes foram submetidos ao protocolo de abertura coronária e exploração dos canais com lima manual tipo K n.15, preparados com instrumentos ProTaper Next (até X3: # 30.07), e submetidos novamente a TCFC (T2); A seguir foram obturados pela técnica híbrida de Tagger com cimento AH Plus, e submetidos a 1000 ciclos de termociclagem simulando um período de 12 meses. Subsequentemente, os espécimes foram distribuídos de acordo com os protocolos de desobturação do canal radicular, em três grupos (n=10): G1- Protaper Universal Retratamento (D1: #30.09; D2: #25.08; D3: #20.07;); G2- Mtwo Retratamento (#25.05) e G3- DRaCe (DR1: #30.10; DR2: #25.04). Após a desobturação, os espécimes foram submetidos novamente à TCFC (T3). Em seguida, foram submetidos ao protocolo de complementação para remoção do material obturador, em três grupos (n=10): G1, G2 e G3: PT next X4: #40.06. A seguir os espécimes foram submetidos novamente à TCFC (T4) para avaliação da área alargada do canal radicular. A média e o desvio padrão das variáveis quantitativas foram obtidas. A normalidade dos dados foi avaliada pelo teste de Kolmogorov-Smirnov. As variáveis foram avaliadas pelo Teste-t para amostras pareadas para avaliar a diferença entre a área desgastada entre o preparo (Tomografia 2) e o retratamento (Tomografia 4). As variáveis foram avaliadas pelo Teste de Análise de Variância (ANOVA) post hoc Tukey para a comparação entre Protaper-R (grupo 1), Mtwo-R (grupo 2) e D- Race (grupo 3). Foram considerados significativos valores de p < 0,05. A análise de variância evidenciou diferença estatisticamente significante em relação aos grupos em canal mesiovestibular em nível 2 mm abaixo de furca p<0,038 e em canal mesiovestibular em nível 4 mm abaixo de furca p<0,005. Evidenciou também diferença estatisticamente significante em relação aos grupos 1, 2 e 3 em canal mesiovestibular em nível 2 mm abaixo de furca após o retratamento p<0,028. A diferença média da área alargada entre o preparo e o retratamento em canais mesiovestibulares comparando os grupos Protaper-R, Mtwo-R e D-race evidenciou diferença estatisticamente significante em todos os grupos (p<0,000 e p<0,029) e em canais mesiolinguais valores entre p<0,000 e p<0,029. Conclui-se que as técnicas de complementação avaliadas aumentaram a área do canal radicular, contribuindo para a remoção do remanescente de material obturador, sendo que o sistema Protaper-R ® permitiu maior desgaste. Embora tenha havido ampliação da área do canal radicular em níveis determinados, nenhuma das técnicas avaliadas foram capazes de remover completamente o material obturador dos canais radiculares / The objective of the present study was to determine the enlarged area after retreatment of the root canal with nickel-titanium instruments in conical beam computed tomography images. Sixty mesial roots of mandibular molars were selected and submitted to concomitant computed tomography (CBCT) in 4 periods of: before preparation (T1), after preparation (T2), after retreatment (T3) and after completing retreatment (T4). After the initial CBCT (T1), the teeth were submitted to the protocol of coronary opening and exploration of channels with manual file type K n.15, prepared with ProTaper Next instruments (up to X3: # 30.07), and again submitted to CBCT); They were then filled by the Tagger hybrid technique with AH Plus cement and submitted to 1000 cycles of thermocycling simulating a period of 12 months. Subsequently, the specimens were distributed according to root canal clearance protocols, in three groups (n = 10): G1 Protaper Universal Retreatment (D1: # 30.09; D2: # 25.08; D3: # 20.07;); G2- Mtwo Retreatment (# 25.05) and G3- DRaCe (DR1: # 30.10; DR2: # 25.04). After disintegration, the specimens were again submitted to TCFC (T3). Afterwards, they were submitted to the complementation protocol to remove the obturator material, in three groups (n = 10): G1, G2 and G3: PT next X4: # 40.06. Afterwards the specimens were again submitted to TCFC (T4) for evaluation of the enlarged area of the root canal. The mean and standard deviation of the quantitative variables were obtained. The normality of the data was evaluated by the Kolmogorov-Smirnov test. The variables were evaluated by the t-Test for paired samples to evaluate the difference between the worn area between the preparation (Tomography 2) and the retreatment (Tomography 4). The variables were evaluated by the Tukey post-hoc ANOVA for the comparison between Protaper- R (group 1), Mtwo-R (group 2) and D-Race (group 3). Values of p <0.05 were considered significant. The analysis of variance showed a statistically significant difference in relation to the groups in mesiobuccal channel at level 2 mm below furca p <0.038 and in mesiobuccal channel at level 4 mm below furca p <0.005. There was also a statistically significant difference in relation to groups 1, 2 and 3 in mesiobuccal channel at level 2 mm below furcation after retreatment p <0.028. The mean difference in the wide area between preparation and retreatment in mesiobuccal canals comparing the Protaper-R, Mtwo-R and D-race groups showed a statistically significant difference in all groups (p <0.000 and p <0.029) and in mesiolinguistic channels values between p <0.000 and p <0.029. It was concluded that the complementation techniques evaluated increased the root canal area, contributing to the removal of the remainder of the obturator material, and the Protaper-R ® system allowed for greater wear. Although there was enlargement of the root canal area at determined levels, none of the techniques evaluated were able to completely remove the obturator material from the root canals

A proposta deste estudo foi avaliar o comportamento mecânico de dois designs de conexão implante/abutment; hexágono externo e triângulo interno, utilizando parafusos convencionais e parafusos experimentais cone morse. O estudo foi dividido em duas fases: na primeira, foi avaliado o efeito do carregamento mecânico na perda de torque dos parafusos. 40 implantes foram utilizados. Os implantes e abutments foram divididos em 4 grupos: Grupo 1: hexágono externo/parafuso convencional (HE); Grupo 2: triângulo interno/parafuso convencional (TI); Grupo 3: hexágono externo/parafuso cone morse (HECM); Grupo 4: triângulo interno/parafuso cone morse (TICM). Os abutments foram instalados em seus respectivos implantes com torque de aperto de 32Ncm; após intervalo de 10 minutos, foram medidos os valores dos torques de desaperto. Os abutments foram instalados novamente com torque de 32Ncm, e após 10 minutos foram carregados mecanicamente, simulando 1 ano de função oral normal; após o carregamento, os torques de desaperto dos parafusos foram medidos novamente. Os dados foram analisados com o teste one-way ANOVA, com nível de significância de p&le;0,05%. Análises por microscopia óptica foram realizadas antes e após os ensaios. Na segunda fase, foi avaliada a resistência à flexão dos conjuntos implante/abutment. Os mesmos 40 conjuntos foram utilizados. Os testes foram realizados em máquina universal de ensaios, com célula de carga de 500 kgf, deslocamento de 1mm/min, e inclinação de 45&deg;. A força máxima de flexão (FMF) e a força de ruptura (FR) foram determinadas. As informações coletadas foram analisadas com o teste one-way ANOVA, para p&le;0,05. Análises por microscopia óptica foram realizadas para estudo dos componentes após os ensaios de resistência flexural. Os resultados sugeriram que houve diferença significante (p=0,000) na pré-carga residual antes e após carregamento mecânico entre os dois tipos de parafuso: os parafusos cone morse apresentaram torques de desaperto significativamente superiores aos apresentados pelos parafusos planos convencionais. Houve diferença significante nos resultados da FMF obtidos pelos parafusos planos convencionais e pelos parafusos cone morse (p=0,011), sendo que os conjuntos implante/abutment com parafusos cone morse apresentaram maior resistência à flexão. Para os resultados da FR houve influência significante do tipo de conexão (p=0,019), com melhores resultados para a conexão triângulo interno. Considerando as limitações deste estudo, concluiu-se que os parafusos cone morse apresentaram maiores torques de desaperto em comparação aos parafusos planos convencionais; que o design da conexão protética não teve influência significante sobre o torque de desaperto dos parafusos; que os parafusos cone morse obtiveram maiores valores de resistência à flexão, e que a conexão em triângulo interno obteve maiores valores para a força de ruptura. / The purpose of this study was to evaluate the mechanical behavior of two implant/abutment connection designs; external hex and internal tri-channel, using conventional screws and experimental conical screws. The study was divided in two parts; the first evaluated the effect of mechanical loading in the torque loss of the screws. 40 implants were used. The implants and abutments were divided in 4 groups: Group 1: external hex/conventional screw (HE); Group 2: tri-channel/conventional screw (TI); Group 3: external hex/conical screw (HECM); Group 4: tri-channel/conical screw (TICM). The abutments were installed in their respective implants with a tightening torque of 32Ncm, after a 10 minute interval, loosening torque were measured. The abutments were installed again with a 32Ncm torque, and after 10 minutes, they were mechanically loaded, simulating 1 year of normal oral function; after loading, loosening torques of the screws were measured again. Data were analyzed with one-way ANOVA test, with significance level of p&le;0,05. Optical microscopy analysis were performed before and after the tests. The second part evaluated the flexural resistance of the implant/abutment assemblies. The same 40 assemblies were used. The tests were performed in an universal testing machine, with a 500kgf load cell, 1mm/min displacement, and 45&deg; angulation. Maximum bending moment (FMF) and rupture force (FR) were determined. Collected information were analyzed with one-way ANOVA test, for p&le;0,05. Optical microscopy analysis were performed for study of the components after the flexural resistance tests. The results suggested that there were significant differences (p=0,000) in the residual preload before and after mechanical loading between the two types of screws: conical screws showed significantly higher loosening torques than conventional flat screws. There were significant differences in the FMF obtained by the conventional flat screws and by the conical screws (p=0,000); the implant/abutment assemblies with conical screws presented higher flexural resistance. For the FR results, there was significant influence of the type of connection (p=0,019); the tri-channel connection presented better results. Considering the limitations of this study, it was concluded that the conical screws presented higher loosening torques compared to conventional flat screws; the design of the implant/abutment connection presented no significant influence on the loosening torques of the screws; conical screws showed higher bending moment values; and the tri-channel connection obtained higher rupture force values.

A proposta deste estudo foi avaliar o comportamento mecânico de dois designs de conexão implante/abutment; hexágono externo e triângulo interno, utilizando parafusos convencionais e parafusos experimentais cone morse. O estudo foi dividido em duas fases: na primeira, foi avaliado o efeito do carregamento mecânico na perda de torque dos parafusos. 40 implantes foram utilizados. Os implantes e abutments foram divididos em 4 grupos: Grupo 1: hexágono externo/parafuso convencional (HE); Grupo 2: triângulo interno/parafuso convencional (TI); Grupo 3: hexágono externo/parafuso cone morse (HECM); Grupo 4: triângulo interno/parafuso cone morse (TICM). Os abutments foram instalados em seus respectivos implantes com torque de aperto de 32Ncm; após intervalo de 10 minutos, foram medidos os valores dos torques de desaperto. Os abutments foram instalados novamente com torque de 32Ncm, e após 10 minutos foram carregados mecanicamente, simulando 1 ano de função oral normal; após o carregamento, os torques de desaperto dos parafusos foram medidos novamente. Os dados foram analisados com o teste one-way ANOVA, com nível de significância de p&le;0,05%. Análises por microscopia óptica foram realizadas antes e após os ensaios. Na segunda fase, foi avaliada a resistência à flexão dos conjuntos implante/abutment. Os mesmos 40 conjuntos foram utilizados. Os testes foram realizados em máquina universal de ensaios, com célula de carga de 500 kgf, deslocamento de 1mm/min, e inclinação de 45&deg;. A força máxima de flexão (FMF) e a força de ruptura (FR) foram determinadas. As informações coletadas foram analisadas com o teste one-way ANOVA, para p&le;0,05. Análises por microscopia óptica foram realizadas para estudo dos componentes após os ensaios de resistência flexural. Os resultados sugeriram que houve diferença significante (p=0,000) na pré-carga residual antes e após carregamento mecânico entre os dois tipos de parafuso: os parafusos cone morse apresentaram torques de desaperto significativamente superiores aos apresentados pelos parafusos planos convencionais. Houve diferença significante nos resultados da FMF obtidos pelos parafusos planos convencionais e pelos parafusos cone morse (p=0,011), sendo que os conjuntos implante/abutment com parafusos cone morse apresentaram maior resistência à flexão. Para os resultados da FR houve influência significante do tipo de conexão (p=0,019), com melhores resultados para a conexão triângulo interno. Considerando as limitações deste estudo, concluiu-se que os parafusos cone morse apresentaram maiores torques de desaperto em comparação aos parafusos planos convencionais; que o design da conexão protética não teve influência significante sobre o torque de desaperto dos parafusos; que os parafusos cone morse obtiveram maiores valores de resistência à flexão, e que a conexão em triângulo interno obteve maiores valores para a força de ruptura. / The purpose of this study was to evaluate the mechanical behavior of two implant/abutment connection designs; external hex and internal tri-channel, using conventional screws and experimental conical screws. The study was divided in two parts; the first evaluated the effect of mechanical loading in the torque loss of the screws. 40 implants were used. The implants and abutments were divided in 4 groups: Group 1: external hex/conventional screw (HE); Group 2: tri-channel/conventional screw (TI); Group 3: external hex/conical screw (HECM); Group 4: tri-channel/conical screw (TICM). The abutments were installed in their respective implants with a tightening torque of 32Ncm, after a 10 minute interval, loosening torque were measured. The abutments were installed again with a 32Ncm torque, and after 10 minutes, they were mechanically loaded, simulating 1 year of normal oral function; after loading, loosening torques of the screws were measured again. Data were analyzed with one-way ANOVA test, with significance level of p&le;0,05. Optical microscopy analysis were performed before and after the tests. The second part evaluated the flexural resistance of the implant/abutment assemblies. The same 40 assemblies were used. The tests were performed in an universal testing machine, with a 500kgf load cell, 1mm/min displacement, and 45&deg; angulation. Maximum bending moment (FMF) and rupture force (FR) were determined. Collected information were analyzed with one-way ANOVA test, for p&le;0,05. Optical microscopy analysis were performed for study of the components after the flexural resistance tests. The results suggested that there were significant differences (p=0,000) in the residual preload before and after mechanical loading between the two types of screws: conical screws showed significantly higher loosening torques than conventional flat screws. There were significant differences in the FMF obtained by the conventional flat screws and by the conical screws (p=0,000); the implant/abutment assemblies with conical screws presented higher flexural resistance. For the FR results, there was significant influence of the type of connection (p=0,019); the tri-channel connection presented better results. Considering the limitations of this study, it was concluded that the conical screws presented higher loosening torques compared to conventional flat screws; the design of the implant/abutment connection presented no significant influence on the loosening torques of the screws; conical screws showed higher bending moment values; and the tri-channel connection obtained higher rupture force values.

Made available in DSpace on 2017-07-21T19:25:55Z (GMT). No. of bitstreams: 1 Vinicius Salem.pdf: 2842532 bytes, checksum: 22444ff7cd1897f8dc66bfd6a1f84a65 (MD5) Previous issue date: 2017-03-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the present work, it is explained in a concise way the Aharonov-Bohm (AB) Efect in the magnetic case. Possible interpretations envolving the phenomena are discussed too, through a carefull review about the theme in literature, in purpose to sumarize the diferent interpretations concerning the possible physical reality of electromagnetic potentials in physics, in special the case of the vector potential, since this work focuses in the magnetic AB eect. Also, the construction and solution of Dirac equation is studied in details for the non-relativistic limit case of an electron possessing anomalous magnetic moment (i.e., g 6=2) in a conical space. For this purpose, the self-adjoint extensions method as developed by Bulla and Gesztesy is used in order to obtain expressions for bound states energies and scattering. The self-adjoint extension parameter obtained in the study of bound states and scattering showed very plausible physical results, consonant with the literature in general, as exposed in detail in chapter four. Finally, it is discussed the role of anomaly of the electron magnetic moment in providing bound states energies, a theme rarely discussed in literature since now. / No presente trabalho, procura-se explicar de forma concisa a fenomenologia do Efeito Aharonov-Bohm (AB) magnético, bem como o sistema aplicado a partículas de spin 1/2. Também são discutidas possíveis interpretações para o fenômeno através de uma cuidadosa revisão sobre o tema na literatura, buscando sumarizar as distintas opiniões sobre a possível realidade física dos potenciais eletromagnéticos, em especial do potencial vetor, uma vez que o foco neste trabalho concentra-se no Efeito AB magnético. Posteriormente,é estudada em detalhes a construção e solução da Equação de Dirac para o caso limite não-relativístico do elétron com anomalia do momento magnético (i.e., g 6= 2) em uma topologia cônica. Para isto é utilizado o método de extensão auto-adjunta de operadores na versão desenvolvida por Bulla e Gesztesy, afím de obter expressões para as energias de estados ligados e espalhamento. O parâmetro de extensão obtido no estudo de estados ligados e espalhamento apresentou resultados físicos consistentes com a literatura em geral. Por fím, o papel da anomalia no momento magnético do elétron em proporcionar estados ligados no sistema é discutido detalhadamente, algo até então pouco abordado na literatura.

Surface Acoustic Waves (SAW) fall under a special category of elastic waves that need a material medium to propagate. The energy of these waves is confined to a limited depth below the surface over which they propagate, and their amplitudes decay with increasing depth. As a consequence of their being a surface phenomenon, they are easily accessible for transduction. Due to this reason, a lot of research has been carried out in the area, which has resulted in two very popular applications of SAW - SAW devices and in Non-Destructive Testing and Evaluation. A major restriction of SAW devices is that the SAW need a piezoelectric medium for generation, propagation and reception. This thesis reports the attempt made to overcome this restriction and utilize the SAW on non-piezoelectric substrates for sensing capabilities. The velocity of the SAW is known to be dependent purely on the material properties, specifically the elastic constants and material density. This dependence is the motivation for the sensor system developed in the present work. Information on the survey of the methods suitable for the generation and reception of SAW on non-piezoelectric substrates has been included in the thesis. This is followed by the theoretical and practical details of the method chosen for the present work - the point source/point receiver method. Advantages of this method include a simple and inexpensive fabrication procedure, easy customizability and the absence of restrictions due to directivity of the SAW generated. The transducers consist of a conically shaped PZT element attached to a backing material. When the piezoelectric material on the transmitter side is electrically excited, they undergo mechanical oscillations. When coupled to the surface of a solid, the oscillations are transferred onto the solid, which then acts as a point source for SAW. At the receiver, placed at a distance from the source on the same side, the received mechanical oscillations are converted into an electrical signal as a consequence of the direct piezoelectric effect. The details of the fabrication and preliminary trials conducted on metallic as well as non-metallic samples are given. Various applications have been envisaged for this relatively simple sensor system. One of them is in the field of pressure sensing. Experiments have been carried out to employ the acoustoelastic property of a flexible diaphragm made of silicone rubber sheet to measure pressure. The diaphragm, when exposed to a pressure on one side, experiences a varying strain field on the surface. The velocity of SAW generated on the stressed surface varies in accordance with the applied stress, and the consequent strain field generated. To verify the acoustoelastic phenomenon in silicone rubber, SAW velocities have been measured in longitudinal and transverse directions with respect to that of the applied tensile strain. Similar measurements are carried out with a pressure variant inducing the strain. The non-invasive nature of this setup lends it to be used for in situ measurement of pressure. The second application is in the field of elastography. Traditional methods of diagnosis to detect the presence of sub-epidermal lesions, some tumors of the breast, liver and prostate, intensity of skin irritation etc have been mainly by palpation. The sensor system developed in this work enables to overcome the restrictive usage and occasional failure to detect minute abnormal symptoms. In vitro trials have been conducted on tissue phantoms made out of poly (vinyl alcohol) (PVA-C) samples of varying stiffnesses. The results obtained and a discussion on the same are presented.

Disertacija yra skirta išnagrinėti ir paaiškinti impulsinių šviesos pluoštų parametrinio stiprinimo metu vykstančius reiškinius. Ypatingas dėmesys yra skiriamas erdvinei-laikinei impulsinio šviesos pluošto dinamikai stiprinimo metu. Visi nagrinėjamų reiškinių tyrimai buvo atliekami taikant skaitmeninio modeliavimo metodus. Modelyje panaudotos lygtys buvo išvestos iš Maksvelo lygčių, išsamiai aptariant lygčių išvedimo metu daromas prielaidas. Naudojantis pateiktu modeliu buvo gauti skaitmeniniai rezultatai, kurie parodė, jog nekolineariame parametriniame stiprintuve, kuomet kaupinimo ir signalinio impulsų frontai nėra sutapatinti, signalinis impulsas tampa pakrypęs ir be kampinės dispersijos taip pat įgyja ir erdvinį čirpą. Nustatyta, kad indukuotų erdvinės ir kampinės dispersijų mažėjimo sparta, didinant signalinio impulso laikinį čirpą, yra skirtinga. Pagrindiniai šio teorinio tyrimo rezultatai buvo patvirtinti eksperimentiškai. Taip pat šioje disertacijoje yra pristatomas naujas ir universalus impulsinių kūginių bangų parametrinio stiprinimo metodas, kuriame sustiprinti impulsai patys susispaudžia laike ir erdvėje paprasčiausiai sklisdami laisvoje erdvėje. Šis metodas leidžia formuoti didelio smailinio intensyvumo invariantiškus bangų paketus, galinčius nusklisti daugelį Relėjaus nuotolių norimoje medžiagoje. Priešingai nei įprastame čirpuotų impulsų stiprinimo metode, šis metodas nereikalauja impulsų spaustuvo, o tai žymiai palengvina parametrinį kelių optinių ciklų... [toliau žr. visą tekstą] / This thesis is aimed to provide an extensive picture of the phenomena encountered in optical parametric amplification of pulsed light beams. The particular attention is paid for the spatio-temporal dynamics of the pulsed light beams being amplified. All the research has been done by means of numerical methods. The equations used in the model were derived from the Maxwell’s equations and the assumptions made along the derivation of equations were discussed. Using the presented model it has been numerically demonstrated, that in noncollinear optical parametric amplifier, when pulse fronts of pump and signal are not matched, the signal pulse becomes tilted and aside from angular dispersion acquires a spatial chirp. It has been shown, that the magnitudes of the induced spatial and angular dispersions decrease at different rates with the increase of the signal pulse temporal chirp. The main results of this study were verified experimentally. Additionally, in this thesis we have proposed a novel and versatile method for pulsed conical wave parametric amplification with subsequent spatio-temporal compression during propagation in free space. It allows to form ultra-intense and propagation invariant wave-packets capable to propagate over many Rayleigh range in the desired material. In contrast to ordinary chirped-pulse amplification technique it does not require a pulse compressor, thus greatly facilitates the parametric amplification of few-cycle light pulses.

This thesis is aimed to provide an extensive picture of the phenomena encountered in optical parametric amplification of pulsed light beams. The particular attention is paid for the spatio-temporal dynamics of the pulsed light beams being amplified. All the research has been done by means of numerical methods. The equations used in the model were derived from the Maxwell’s equations and the assumptions made along the derivation of equations were discussed. Using the presented model it has been numerically demonstrated, that in noncollinear optical parametric amplifier, when pulse fronts of pump and signal are not matched, the signal pulse becomes tilted and aside from angular dispersion acquires a spatial chirp. It has been shown, that the magnitudes of the induced spatial and angular dispersions decrease at different rates with the increase of the signal pulse temporal chirp. The main results of this study were verified experimentally. Additionally, in this thesis we have proposed a novel and versatile method for pulsed conical wave parametric amplification with subsequent spatio-temporal compression during propagation in free space. It allows to form ultra-intense and propagation invariant wave-packets capable to propagate over many Rayleigh range in the desired material. In contrast to ordinary chirped-pulse amplification technique it does not require a pulse compressor, thus greatly facilitates the parametric amplification of few-cycle light pulses. / Disertacija yra skirta išnagrinėti ir paaiškinti impulsinių šviesos pluoštų parametrinio stiprinimo metu vykstančius reiškinius. Ypatingas dėmesys yra skiriamas erdvinei-laikinei impulsinio šviesos pluošto dinamikai stiprinimo metu. Visi nagrinėjamų reiškinių tyrimai buvo atliekami taikant skaitmeninio modeliavimo metodus. Modelyje panaudotos lygtys buvo išvestos iš Maksvelo lygčių, išsamiai aptariant lygčių išvedimo metu daromas prielaidas. Naudojantis pateiktu modeliu buvo gauti skaitmeniniai rezultatai, kurie parodė, jog nekolineariame parametriniame stiprintuve, kuomet kaupinimo ir signalinio impulsų frontai nėra sutapatinti, signalinis impulsas tampa pakrypęs ir be kampinės dispersijos taip pat įgyja ir erdvinį čirpą. Nustatyta, kad indukuotų erdvinės ir kampinės dispersijų mažėjimo sparta, didinant signalinio impulso laikinį čirpą, yra skirtinga. Pagrindiniai šio teorinio tyrimo rezultatai buvo patvirtinti eksperimentiškai. Taip pat šioje disertacijoje yra pristatomas naujas ir universalus impulsinių kūginių bangų parametrinio stiprinimo metodas, kuriame sustiprinti impulsai patys susispaudžia laike ir erdvėje paprasčiausiai sklisdami laisvoje erdvėje. Šis metodas leidžia formuoti didelio smailinio intensyvumo invariantiškus bangų paketus, galinčius nusklisti daugelį Relėjaus nuotolių norimoje medžiagoje. Priešingai nei įprastame čirpuotų impulsų stiprinimo metode, šis metodas nereikalauja impulsų spaustuvo, o tai žymiai palengvina parametrinį kelių optinių ciklų... [toliau žr. visą tekstą]

This thesis describes and develops two experimental techniques, Time Resolved Photoelectron Spectroscopy (TRPES), and Time Resolved Coincidence Imaging Spectroscopy (TRCIS), to study ultrafast gas phase chemical dynamics. We use TRPES to investigate the effects of methyl substitution on the electronic dynamics of the simple alpha, beta-enones acrolein, crotonaldehyde, methylvinylketone, and methacrolein following excitation to the S2 state. We determine that following excitation, the molecules move rapidly away from the Franck-Condon region reaching a conical intersection promoting relaxation to the S1 state. Once on the S1 surface, the trajectories access another conical intersection leading them to the ground state. Only small variations between molecules are seen in their S2 decay times. However, the position of methyl group substitution greatly affects the relaxation rate from the S1 surface. Ab initio calculations used to compare the geometries, energies, and topographies of the S1/S0 conical intersections of the molecules are not able to explain the variations in relaxation behaviour. We propose a model that uses dynamical factors of specific motions in the molecules to explain the differing nonadiabatic S1/S0 crossing rates. The second part of this thesis examines the issues involved with design and construction of a Coincidence Imaging Spectrometer. This type of spectrometer measures the 3-dimensional velocities of both photoelectrons and photoions generated from probing of laser induced photodissociation reactions. Importantly, the photoelectrons and photoions are measured in coincidence from single molecules, enabling measurements such as recoil frame photoelectron angular distributions and correlated photoelectron/photoion energy maps, inaccessible using existing techniques. How to optimize the spectrometer resolution through design, tuning, and calibration is discussed. The power of TRCIS is demonstrated with the investigation of the photodissociation dynamics of the NO dimer. TRPES experiments first identified a sequential kinetic model following 209nm excitation resulting in NO(X) (ground state) and NO(A) (excited state) products. Using TRCIS, it was possible to measure time resolved vibrational energy distributions of the products, indicating the extent of vibrational energy redistribution within the dimers prior to dissociation. Recoil frame photoelectron angular distributions and theoretical support allow identification of a previously disputed intermediate on the dissociation pathway. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-04-01 10:12:39.968