Von generellem Interesse für potentielle Anwendungsmöglichkeiten sind Materialien mit speziellen elektrischen bzw. nichtlinearen optischen Eigenschaften. Im Rahmen dieser Arbeit wurden neue dipolare Verbindungen synthetisiert und charakterisiert, welche eine zentrale Organosilanspacereinheit (-SiMex-,-(SiMe2)6-), ein terminales Metallkomplexfragment (potentieller Donor, FcN-) sowie eine terminale organische Akzeptoreinheit (-PhF, -PhBr, -PhCHO) enthalten und gleichzeitig eine große Variationsbreite gewünschter Eigenschaften aufweisen. Aus Photo-EMK-Messungen, UV/VIS-, NMR-Spektroskopie, Mößbauer- und cyclovoltammetrischen Untersuchungen kann auf eine im Festkörper auftretende temperaturabhängig variierende intermolekulare Kopplung zwischen dem Donor und dem organischen Akzeptor geschlossen werden. Photo-EMK- und Einkristallröntgenstrukturanalysen der Salze (Hydrochloride, Pikrate) offenbaren starke intermolekulare Wechselwirkungen (C-H···π, D-C-H···A) mit entscheidendem Einfluß auf Festkörpereigenschaften (supramolekulare MO's).

This thesis presents the measurement of the differential cross section of Z boson pro-duction in association with jets (Z+jets) in proton-proton collision at the center-of-massenergy of 13 TeV. The data has been recorded with the CMS detector at the LHC duringthe year 2015, corresponding to an integrated luminosity of 2.19 fb −1 .A study of theCMS muon High Level Trigger (HLT) with the data collected in 2016 is also presented.The goal of analysis is to perform a first measurement at 13 TeV of the cross sections ofZ+jets as a function of the jet multiplicity, its dependence on the transverse momentumof the Z boson, the jet kinematic variables (transverse momentum and rapidity), thescalar sum of the jet momenta, and the balance in the transverse momentum betweenthe reconstructed jet recoil and the Z boson. The results are obtained by correctingthe detector effects, and are unfolded to particle level. The measurement are com-pared to four predictions using different approximations: at the leading-order (LO),next-to-leading-order (NLO) and next-to-next-to-leading order (NNLO) accuracy. Thefirst two calculations used M AD G RAPH 5_ A MC@NLO interfaced with PYTHIA 8 for theparton showering and hadronisation, one of which includes matrix elements (MEs) atLO, another includes one-loop corrections (NLO). The third is a fixed-order calculationwith NNLO accuracy for Z+1 jet using the N -jettiness subtraction scheme (N jetti ). Thefourth uses the GENEVA program with an NNLO calculation combined with higher-order resummation.A series of studies on the HLT double muon trigger are also included. Since 2015 theLHC reached higher luminosity, more events are produced inside the CMS detector persecond, which resulted in more challenges for the trigger system. The work presentedincludes the monitoring, validation and the calibration of the muon trigger paths since2016. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Von generellem Interesse für potentielle Anwendungsmöglichkeiten sind Materialien mit speziellen elektrischen bzw. nichtlinearen optischen Eigenschaften. Im Rahmen dieser Arbeit wurden neue dipolare Verbindungen synthetisiert und charakterisiert, welche eine zentrale Organosilanspacereinheit (-SiMex-,-(SiMe2)6-), ein terminales Metallkomplexfragment (potentieller Donor, FcN-) sowie eine terminale organische Akzeptoreinheit (-PhF, -PhBr, -PhCHO) enthalten und gleichzeitig eine große Variationsbreite gewünschter Eigenschaften aufweisen. Aus Photo-EMK-Messungen, UV/VIS-, NMR-Spektroskopie, Mößbauer- und cyclovoltammetrischen Untersuchungen kann auf eine im Festkörper auftretende temperaturabhängig variierende intermolekulare Kopplung zwischen dem Donor und dem organischen Akzeptor geschlossen werden. Photo-EMK- und Einkristallröntgenstrukturanalysen der Salze (Hydrochloride, Pikrate) offenbaren starke intermolekulare Wechselwirkungen (C-H···π, D-C-H···A) mit entscheidendem Einfluß auf Festkörpereigenschaften (supramolekulare MO's).

Lasers are increasingly used for a wide range of different applications for both civil and military purposes. Due to the distinct properties of laser light, use of lasers often comes with a risk of damage to the human eye and other optical sensors. Therefore, an effective laser protection is needed. 2D-materials is a relatively new class of materials, which have shown to possess many unique properties compared to its bulk counterparts. Some 2D-materials exhibit nonlinear optical (NLO) properties, and specifically optical power limiting (OPL) effects, and have therefore been researched for laser protection applications. In this work, two different 2D-materials, MXene Ti3C2 and graphene oxide (GO), have been combined with a hybrid organic-inorganic polymer, a so called melting gel (MG), to synthesise nanocomposites possessing OPL effects for laser protection applications. Different methods of incorporating the 2D-materials in the polymer matrix as well as the effect on optical properties of different concentrations of 2D-materials were investigated. The prepared nanocomposites were characterised using optical microscopy, spectroscopy and OPL measurements in order to investigate and quantify their linear and nonlinear optical properties. The MG was optically clear, mechanically stable and easy to synthesise, which makes it a suitable candidate as a matrix for a laser protection nanocomposite. Additionally, it was possible to dope the MG with the two different 2D-materials to create nanocomposites showing desirable optical properties in the visible spectrum. However, many samples showed signs of clustered 2D-particles indicating that the dispersion could be improved. Finally, OPL measurements, performed at 532 nm, showed that the MG itself exhibited OPL effects, both 2D-materials showed a stronger OPL effect than the non-doped MG and that GO-doped samples gave a better protection than the MXene samples.

Des recherches très importantes ont été dédiées à l'étude des composés ferroélectriques de type bronze de tungstène quadratique (TTB). Cette thèse concerne la synthèse et la caractérisation de 7 matériaux TTB de formule générale A6M2M'8O30 (A = Sr2+, Ba2+ ou Pb2+, M = Ti4+, Zr4+ ou HF4+; M' = Nb5+ ou Ta5+). Ces composés cristallins de grande taille ∼100 nm ont été synthétisés sous forme de poudre. Les moyennes expérimentales : diffractions des rayons X, spectroscopie Raman, la microscopie électronique MEB et MET, l'optique non linéaire ONL, ont permis d'établir des relations étroites entre structure et propriétés physiques. Les susceptibilités optiques non linéaires de 2eme et 3eme ordres, χ(2), χ(3) de chaque composés ont été déterminées et les valeurs résultantes du χ(3) ne montrent pas les mêmes caractéristiques que χ(2), car le signal de THG est moins dépendant de structure que SHG qui requiert un milieu non-centrosymétrique. Le décalage fréquentiel (Δσ) des modes de vibrations entre les structures à base de strontium(Sr) et celles à base de Barium(Ba) a été constaté afin d'identifier les signatures propres de ces composés. L'interprétation de ces poudres n'était pas facile car les pics sont très délicats. Nos mesures expérimentales montrent clairement que les positions des pics peuvent être modifiées par le changement cationique au sein des matériaux, plus la maille cristalline est rigide, plus on a des pics plus discernables. La différence est nettement visible là ou l'émission est autour de 808 cm-1 pour la structure (Sr), alors que pour le (Br) elle est autour de 780cm-1. Nous attribuons ce Δσ (28cm-1) à la transition de groupe de symétrie spatiale de Pba2 vers P4bm. L'ensemble des résultats décrits dans ce travail ont montrés la grande variété des paramètres sur lesquels il est possible d'agir afin d'optimiser les compositions en vue d'une application spécifique. / Recently, very significant research has been devoted to the study of ferroelectric compounds of tetragonal tungsten bronze (TTB). This thesis deals with the synthesis and characterization of 7 TTB's material with general formula A6M2M'8O30 (A = Sr2+, Ba2+ or Pb2+, M = Ti4+, Zr4+ or HF4+, M '= Nb5+ or Ta5+). These crystalline compounds of large size ~ 100 nm were synthesized in powder form. The experimental Technics: X-ray diffraction, Raman spectroscopy, scanning electron microscopy SEM and TEM and nonlinear optics NLO, allowed us to establish close relationships between structure and physical properties. The nonlinear 2nd and 3rd order optical susceptibility χ(2), χ(3) of all compounds were determined and the resulting values of χ(3) did not show the same characteristics as measures of χ(2) because the THG signal is less dependent on the structure where SHG signal requires a non-centro-symmetric medium. The frequency shift between the vibration modes of structures containing strontium (Sr) and those based on Barium (Ba) has been detailed to identify signatures of these specific compounds. The interpretation of these powders wasn't that easy as these peaks are very delicate but our experimental results clearly show that the positions of the peaks can be modified by the change in cation materials, as long as the crystal lattice is more rigid, more we get discernible Raman modes. This difference is clearly visible where the emission is around 808 cm-1 for the structure Sr, whereas the Br it is centered around 780cm-1. We attribute these Δσ (28cm-1) to the transition of spatial symmetry group from Pba2 to P4bm. Results showed the wide variety of settings in which it is possible to act in order to optimize the compositions for a specific application.

Le travail effectué dans cette thèse présente diverses études théoriques et phénoménologiques du processus de production exclusive de mésons vecteurs rho neutres polarisés longitudinalement dans les collisions entre photons virtuels, dans le cadre de la chromodynamique quantique (QCD). La virtualité des photons permet de situer notre approche dans le secteur perturbatif de la théorie. Les régimes cinématiques envisagés mènent à l'utilisation d'outils théoriques variés qui font apparaître différentes propriétés de factorisation de l'amplitude de diffusion: deux types de factorisation colinéaire (à courte distance) pour ce processus sont discutés au chapitre 1, faisant apparaître –suivant la polarisation des photons virtuels et le régime cinématique considéré- des Amplitudes de Distribution Généralisées (GDA) ou des Amplitudes de Distribution de Transition (TDA), outils communément utilisés dans la description des processus exclusifs. Nous introduisons dans le Chapitre 2 de manière autocohérente les bases du formalisme BFKL valide dans la limite à haute énergie (limite de Regge) de QCD, en vue de son utilisation phénoménologique détaillée dans le Chapitre 3: l'amplitude de diffusion du processus est décrite dans ce formalisme en exploitant la factorisation dans l'espace bidimensionnel des impulsions transverses, ou kT-factorisation. Nous prédisons la valeur de la section efficace du processus à l'ordre de Born de la resommation BFKL et nous discutons de son observation possible auprès du futur collisionneur linéaire international (ILC). Nous obtenons également les sections efficaces différentielles du processus sans transfert d'impulsion avec resommation BFKL complète à l'ordre des logarithmes dominants (Leading-Order) ainsi qu'à l'ordre suivant (Next-to-Leading-Order) afin d'établir un test fin du processus d'échange d'un Poméron dur décrit par le formalisme BFKL, observable au futur collisionneur linéaire ILC.

NLO materials have been researched for nearly five decades from the point of view of understanding the basic mechanisms and also in the pursuit of new materials possessing improved properties. Materials satisfying a set of physico-chemical properties such as wide transmission range, good mechanical hardness, high po-larizablity, noncentric crystal structure, good chemical stability, etc are the ones which are sought after. Several organic and inorganic molecules have been synthe-sized with the hope of finding materials that possess the desired NLO properties. Most of the organic materials are known to possess high figure of merit. However, their poor mechanical strength and needle like growth habit are hindrances to practical applications. Inorganic NLO materials have better mechanical properties but many of them possess small deff and laser induced damage threshold. Semi-organic NLO materials are intended to have the merits of both organic and inorganic counterparts. In this investigation, three important NLO crystals, viz cesium hydrogen L-malate monohydrate (CsLM, CsH[C4H4O5]H2O), cesium lithium borate(CLBO,CsLiB6O10)and near stoichiometric lithium niobate codoped with Nd and Zn (Nd:Zn:LiNbO3)are chosen for detailed study. The thesis is organized into 6 chapters. First chapter contains the theoretical background of the physical and chemical phenomena including a review of nonlin-ear optics, second harmonic generation, multiphoton absorption & refraction con-cepts, single crystal growth, principles of ferroelectricity and the scope of the work involved. For better connectivity, a brief review of the earlier work carried out on the chosen materials is given in the beginning of each chapter. The second chapter discusses the methodology of work and experimental details used in the present study. The third chapter deals with studies on CsLM, the new organometallic NLO crystal. Its structure, electro-optical properties and dielectric properties in FIR region are reported very recently. This material is also reported to show a phase transition at 50 0C though not much is understood about its nature. Further details of crystal growth conditions, nonlinear optical properties and laser damage thresholds are little known on this newly discovered NLO material. In this chapter detailed crystal growth studies and investigations of physical properties are presented. During growth, CsLM crystals manifest in platy and prismatic morphologies depending on level of super saturation invoked. The maximum dimensions of the grown crystal are 20 x15 x35 mm3. It has very good transmission in the range, 250-1300 nm and dislocation density of ≈104/cm2 . The dc conductivity measurements place this crystal between an ionic conductor and a dielectric. Dielectric properties show considerable frequency dispersion and axial anisotropy with є′ being the highest along the polar b axis. Maker fringes experiment reveals that CsLM possesses good second harmonic generation efficiency, an order of magnitude higher than KDP. It also has high laser damage threshold for fundamental and second harmonic wavelengths of Nd:YAG pulsed laser. TGA/DTA experiments are performed on the crystals grown below and above the reported transition temperature(labelled as CsLM and Anhydrous-CsLM respectively). The present investigations on Anhydrous-CsLM show that it crystallizes in a structure different from that of CsLM and the nature of the reported ′phase transition ′is driven by sluggish hydration and dehydration processes. Recently UV transparent nonlinear optical materials were evaluated for the fab-rication of all solid state UVlasers and CLBO is one such NLO material. It crystal-lizes in non-centrosymmetric tetragonal space group, I42d. It is highly transparent in the wide range of wavelengths from 180 to 2500 nm and has good deff. It pos-sesses very good angular and spectral bandwidth tolerances compared to its contemporaries such as lithium triborate(LBO) and beta barium borate(β-BBO). There is, however, a problem associated with this material that it cracks when exposed to atmosphere due to its hygroscopic nature. This chapter details the fabrication of the required instrumentation to grow single crystals of this material and the study of possible solutions to avoid cracking problem besides its new nonlinear properties. Since the melts of borate materials are known to be highly viscous, the crystal growth apparatus should have the options for tuning the parameters like seed and crucible rotation rates, temperature isotherms, slow pulling rate, etc. Keeping the above in mind, a high temperature top seeded solution growth unit was designed and fabricated inhouse. Highly transparent single crystals of CLBO were grown using the above unit which were characterized for the defects/dislocations using X-ray topography. The average dislocation density estimated is ≈103/cm2. The nonlinear optical absorption(NLA) and refraction(NLR) properties are studied. Z-scan experiments reveal that five photon absorption(5PA )is responsible for nonlinear absorption when the wavelength and pulse width are 800 nm and 110 fs respectively. For 532 nm and 6 ns pulses, dielectric breakdown occurs before NLA could occur due to high pulse influence. CLBO is found to show negative nonlinear refraction under high intensities. Hygroscopicity of CLBO is attributed to the entry of water through the channels that are present along a and b axes, which in turn, cause cracking. Doping, is expected to modify the size of the channels. Since certain dopants are found to improve the stability of CLBO, substitution of Cs site with Zn and Gd is carried out to reduce the size of channels. As there was no significant improvement with doping experiments, an alternate approach is attempted by coating with SiO2 thin films on the optical elements to prevent the water molecules from entering lattice through the channels. The results and discussion of the above studies are presented in the chapter 4. Lithium niobate is the most widely used single crystal for fabricating optical modulators, waveguides, SAW devices and optical parametric oscillators. Although single crystals of this ferroelectric material were grown way back in 1965 by Ball-man and Fedulov independently, most of the work till the beginning of 90’s was concentrated on crystals with congruent composition(CLN) because there were no suitable methods available for growing homogeneous single crystals of stoichiomet-ric lithium niobate(SLN). Recently, Double Crucible Czochralski method with au-tomatic powder feeding technique and top seeded solution growth technique with Li2O and K2O fluxes are shown to produce SLN crystals. In this work, top seeded solution growth technique with58.6 mol% Li2O composition(self flux) is adopted to grow SLN crystals and the details of the growth and investigations are presented in chapter 5. Initially, crystal growth of SLN, and Zn & Nd codoped SLN are de-scribed. The maximum dimesions of the SLN crystals are 20 mm diameter and 35 mm length. CLN crystals(30mm diameter and 70 mm length) are also grown for comparison. The growth rate for SLN crystals is approximately 25 times lower than that for CLN. The maximum amount of Zn added to the melt is 2.5 mol%. For Nd codoping, four concentrations (0.2, 0.5, 0.9, 1.5 mol%) have been chosen with Zn concentration in the melt fixed at 2.5 mol%. Addition of Zn is to enhance the pho-torefractive damage threshold and Nd to use SLN as laser host. Structural studies on the grown crystals using powder X-ray diffraction show no additional phases. The domain structure analysis by chemical etching studies reveal that it is sensitive to doping and temperature gradient above the melt surface. The grown crystals possess good transmission in the UV-Vis-NIR region. Apparent increase in the dielectric constant found in doped crystals is attributed to space charge effect. In Nd:Zn codoped SLN, the parameters corresponding to lasing (Judd-Ofelt parameters, radiative transition probabilities, branching ratios) have been evaluated and found to be better than those obtained for codoped CLN. Surface laser damage and photorefractive damage thresholds are enhanced by 2 and 4 orders of magnitude respectively for the crystals grown with 2.5 mol% Zn in the melt. Nonlinear absorption and refraction studies using femtosecond Z-scan experiments reveal a correlation between the nonstoichiometric defects and nonlinear absorption & refraction coefficients. Polarization switching studies carried out on pure and Zn doped samples indicate an enhancement in switching rate at elevated temperatures. In the sixth and final chapter, a comprehensive summary of the present work and the scope for further investigations related to this work are given.

Transition metal compounds, especially the oxides, containing dn (0 ≤ n ≤ 10) electronic configuration, constitute the backbone of solid state/materials chemistry aimed at realization of novel materials properties of technological importance. Some of the significant materials properties of current interest are spin-polarized metallic ferromagnetism, negative thermal expansion, second harmonic nonlinear optical (NLO) susceptibility, fast ionic and mixed electronic/ionic conductivity for application in solid state batteries, and last but not the least, high-temperature superconductivity. Typical examples for each one of these properties could be found among transition metal oxides. Thus, alkaline-earth metal (A) substituted rare-earth (Ln) manganites, Lnı.xAxMnΟ3, are currently important examples for spin-polarized magnetotransport, ZrV2O7 and ZrW2O8 for negative thermal expansion coefficient, KTiOPO4 and LiNbO3 for second harmonic NLO susceptibility, (Li, La) TiO3 and LiMn2O4 for fast-ionic and mixed electronic/ionic conductivity respectively, and the whole host of cuprates typified by YBa2Cu3O7 for high Tc superconductivity. Solid state chemists constantly endeavour to obtain structure-property relations of solids so as to be able to design better materials towards desired properties. Synthesis coupled with characterization of structure and measurement of relevant properties is a common strategy that chemists adopt for this task. The work described in this thesis is based on such a broad-based chemists' approach towards understanding and realization of novel materials properties among the family of metal oxides. A search for metallic ferro/ferrimagnetism among the transition metal perovskite oxides, metallicity and possibility of superconductivity among transition-metal substituted cuprates and second order NLO susceptibility among metal oxides containing d° cations such as Ti(IV), V(V) and Nb(V) - constitute the main focus of the present thesis. New synthetic strategies that combine the conventional ceramic approach with the chemistry-based 'soft1 methods have been employed wherever possible to prepare the materials. The structures and electronic properties of the new materials have been probed by state-of-the art techniques that include powder X-ray diffraction (XRD) together with Rietveld refinement, electron diffraction, thermogravimetry, measurement of magnetic susceptibility (including magnetoresistance), Mossbauer spectroscopy and SHG response (towards 1064 nm laser radiation), besides conventional analytical techniques for determination of chemical compositions. Some of the highlights of the present thesis are: (i) synthesis of new mixed valent [Mn(III)/Mn(IV)] perovskite-type manganites, ALaMn2O6-y (A = K, Rb) and ALaBMn3O9_y (A = Na, K; B = Ca, Sr) that exhibit ferromagnetism and magnetoresistance; (ii) investigation of a variety of ferrimagnetic double-perovskites that include ALaMnRuO6 (A = Ca, Sr, Ba) and ALaFeVO6 (A = Ca, Sr) and A2FeReO6 (A = Ca, Sr, Ba) providing new insights into the occurrence of metallic and nonmetallic ferrimagnetic behaviour among this family of oxides; (iii) synthesis of new K2NiF4-type oxides, La2-2xSr2XCui.xMxO4 (M = Ti, Mn, Fe, Ru) and investigation of Cu-O-M interaction in two dimension and (iv) identification of the structural rnotif(s) that gives rise to efficient second order NLO optical (SHG) response among d° oxides containing Ti(IV), V(V), Nb(V) etc., and synthesis of a new SHG material, Ba2-xVOSi2O7 having the fresnoite structure. The thesis consists of five chapters and an appendix, describing the results of the investigations carried out by the candidate. A brief introduction to transition metaloxides, perovskite oxides in particular, is presented in Chapter 1. Attention is focused on the structure and properties of these materials. Chapter 2 describes the synthesis and investigation of two series of anion-deficient perovskite oxides, ALaMn2O6-y (A = K, Rb, Cs) and ALaBMn3O9_y (A = Na, K; B = Ca, Sr). ALaMn2O6-y (A = K, Rb, Cs) series of oxides adopt 2 ap x 2 ap superstructure for K and Rb phases and √2 av x √2 ap x 2 ap superstructure (ap = perovskite subcell) for the Cs phase. Among ALaBMn3O9-y phases, the A = Na members adopt a new kind of perovskite superstructure, ap x 3 ap, while the A = K phases do not reveal an obvious superstructure of the perovskite. All these oxides are ferromagnetic (Tc ~ 260-325 K) and metallic exhibiting a giant magnetoresistance behaviour similar to alkaline earth metal substituted lanthanum manganites, Lai_xAxMnO3. However, unlike the latter, the resistivity peak temperature Tp for all the anion-deficient manganites is significantly lower than Tc. In Chapter 3, we have investigated structure and electronic properties of double-perovskite oxides, A2FeReO6 (A = Ca, Sr and Ba). The A = Sr, Ba phases are cubic (Fm3m) and metallic, while the A = Ca phase is monoclinic (P2yn) and nonmetallic. All the three oxides are ferrimagnetic with Tcs 315-385 K as reported earlier. A = Sr, Ba phases show a negative magnetoresistance (MR) (10-25 % at 5 T), while the Ca member does not show an MR effect. 57Fe Mossbauer spectroscopy shows that iron is present in the high-spin Fe3+ (S = 5/2) state in Ca compound, while it occurs in an intermediate state between high-spin Fe2+ and Fe3+ in the Ba compound. Monoclinic distortion and high covalency of Ca-O bonds appear to freeze the oxidation states at Fe+3/Re5+ in Ca2FeRe O6, while the symmetric structure and ionic Ba-O bonds render the FeReO6 array highly covalent and Ba2FeReO6 metallic. Mossbauer data for Sr2FeReO6 shows that the valence state of iron in this compound is intermediate between that in Ba and Ca compounds. It is likely that Sr2FeReO6 which lies at the boundary between metallic and insulating states is metastable, phase-seperating into a percolating mixture of different electronic states at the microscopic level. In an effort to understand the occurrence of metallicity and ferrimagnetism among double perovskites, we have synthesized several new members : ALaMnFeO6 (A = Ca, Sr, Ba), ALaMnRuO6 (A = Ca, Sr, Ba) and ALaVFeO6 (A = Ca, Sr) (Chapter 3). Electron diffraction reveals an ordering of Mn and Ru in ALaMnRuO6 showing a doubling of the primitive cubic perovskite cell, while ALaVFeO6 do not show an ordering. ALaMnRuOs are ferrimagnetic (Tcs ~ 200-250 K) semiconductors, but ALaVFeO6 oxides do not show a long range magnetic ordering . The present work together with the previous work on double perovskites shows that only a very few of them exhibit both metallicity and ferrimagnetism, although several of them are ferrimagnetic. For example, among the series Ba2MReO6 (M = Mn, Fe, Co, Ni), only the M = Fe oxide is both metallic and ferrimagnetic, while M = Mn and Ni oxides are ferrimagnetic semiconductors. Similarly, A2CrMoO6 (A = Ca, Sr), A2CrRe06 (A = Ca, Sr), and ALaMnRuO6 (A = Ca, Sr, Ba) are all ferrimagnetic but not metallic. While ferrimagnetism of double perovskites arise from an antiferromagnetic coupling of B and B' spins through the B-O-B' bridges, the occurrence of metallicity seems to require precise matching of the energies of d-states of B and B' cations and a high covalency in the BB'O6 array that allows a facile electron-transfer between B and B', Bn++B’m+↔B(n+1)++B’(m-1)+ without an energy cost, just as occurs in ReO3 and other metallic ABO3 perovskites. In an effort to understand the Cu-O-M (M = Ti, Mn, Fe, Ru) electronic interaction in two dimension, we have investigated K2N1F4 oxides of the general formula La2-2xSr2XCui.xMxO4 (M = Ti, Mn, Fe or Ru). These investigations are described in Chapter 4. For M = Ti, only the x = 0.5 member could be prepared, while for M = Mn and Fe, the composition range is 0 < x < 1.0, and for M = Ru, the composition range is 0 < x ≤ 0.5. There is no evidence for ordering of Cu(II) and M(IV) in the x = 0.5 members. While the members of the M = Ti, Mn and Ru series are semiconducting/insulating, the members of the M = Fe series are metallic, showing a broad metal-semiconductor transition around 100 K for 0 < x ≤ 0.15 that is possibly related to a Cu(II)-O-Fe(IV) < > Cu(III)-O-Fe(III) valence degeneracy. Increasing the strontium content at the expense of lanthanum in La2-2xSr2XCui.xFexO4 for x ≤ 0.20 renders the samples metallic but not superconducting. In a search for inorganic oxide materials showing second order nonlinear optical (NLO) susceptibility, we have investigated several borates, silicates and phosphates containing /ram-connected MO6 octahedral chains or MO5 square-pyramids, where M = d°: Ti(IV), Nb(V) or Ta(V). Our investigations, which are described in Chapter 5, have identified two new NLO structures: batisite, Na2Ba(TiO)2Si4O12, containing trans-connectd TiO6 octahedral chains, and fresnoite, Ba2TiOSi2O7, containing square-pyramidal T1O5. Investigation of two other materials containing square-pyramidal TiO5, viz., Cs2TiOP2O7 and Na4Ti2Si8O22. 4H2O, revealed that isolated TiO5 square-pyramids alone do not cause a second harmonic generation (SHG) response; rather, the orientation of T1O5 units to produce -Ti-O-Ti-O- chains with alternating long and short Ti-0 distances in the fresnoite structure is most likely the origin of a strong SHG response in fresnoite. Indeed, we have been able to prepare a new fresnoite type oxide, Ba2.xVOSi2O7 (x ~ 0.5) that shows a strong SHG response, confirming this hypothesis. In the Appendix, we have described three synthetic strategies that enabled us to prepare magnetic and NLO materials. We have shown that the reaction CrO3 + 2 NH4X > CrO2 + 2 NH3 + H2O + X2 (X = Br, I), which occurs quantitatively at 120-150 °C, provides a convenient method for the synthesis of CrO2. Unlike conventional methods, the method described here does not require the use of high pressure for the synthesis of this technologically important material. For the synthesis of magnetic double perovskites, we have developed a method that involves reaction of basic alkali metal carbonates with the acidic oxides (e.g. Re2O7) first, followed by reaction of this precursor oxide with the required transition metal/transition metal oxide (e.g. Fe/Fe2O3). By this method we have successfully prepared single-phase perovskite oxides, A2FeReO6, ACrMoO6 and ALaFeVO6. We have prepared the new NLO material Ba2_xV0Si207 from Ba2VOSi2O7 by a soft chemical redox reaction involving the oxidation of V(IV) to V(V) using Br2 in CH3CN/CHCI3. Ba2V0Si207 + 1/2 Br2 > Bai.5V0Si207 + 1/2 BaBr2. The work presented in this thesis was carried out by the candidate as part of the Ph.D. training programme. He hopes that the studies reported here will constitute a worthwhile contribution to the solid state chemistry of transition metal oxides and related materials.

Ο όρος μη-γραμμική οπτική αντιπροσωπεύει τον κλάδο της οπτικής ο οποίος μελετά την αλληλεπίδραση της ύλης με ακτινοβολία πολύ ισχυρής έντασης. Όταν ένα υλικό εκτεθεί σε ακτινοβολία υψηλής έντασης όπως αυτή του laser, οι οπτικές του ιδιότητες αλλάζουν εξαιτίας της πόλωσης που επάγεται στα δομικά υλικά του και το αποτέλεσμα είναι η αλλαγή των οπτικών του ιδιοτήτων. Αυτό με τη σειρά του οδηγεί σε μία πληθώρα φαινομένων τα οποία μας βοηθούν στη κατανόηση της δομής του υλικού άλλα και των φυσικών μηχανισμών που κρύβονται πίσω από αυτά. Υλικά με μεγάλες μη-γραμμικες οπτικές ιδιότητες είναι πολύ χρήσιμα στην έρευνα και την ανάπτυξη πολλών κλάδων της τεχνολογίας. Σαν παράδειγμα μπορεί να αναφερθεί η ανάπτυξη των οπτικών και κβαντικών υπολογιστών, αλλά και τεχνολογιών οι οποίες μπορούν να βρουν εφαρμογή στις τηλεπικοινωνίες. Στη παρούσα εργασία μελετώνται οι μη-γραμμκές οπτικές ιδιότητες υλικών με μορφή διαλυμάτων. Η διάρθρωση της εργασίας είναι ως εξής: Στο πρώτο κεφάλαιο γίνεται μία εισαγωγή και παρουσιάζονται κάποιες βασικές έννοιες της μη-γραμμικής οπτικής. Έπειτα παρουσιάζεται ο τρόπος που μπορούν να εξαχθούν οι σχέσεις οι οποίες περιγράφουν τις μη-γραμμικές οπτικές ιδιότητες των υλικών όπως τη μη-γραμμική επιδεκτικότητα τρίτης τάξης με βάση τη κλασσική Φυσική και τη κβαντομηχανική. Το κεφάλαιο κλείνει παρουσιάζοντας μερικά φαινόμενα τα οποία οφείλονται στη μη-γραμμική επιδεκτικότητα τρίτης τάξης. Στο δεύτερο κεφάλαιο γίνεται η παρουσίαση των πειραματικών τεχνικών που χρησιμοποιήθηκαν για τη διεξαγωγή των πειραμάτων, αλλά και η διαδικασία που ακολουθήθηκε για την εξαγωγή των μη-γραμμικών οπτικών ιδιοτήτων από τα πειραματικά δεδομένα. Στα κεφάλαια που ακολουθούν παρουσιάζονται τα πειραματικά αποτελέσματα των συστημάτων που μελετήθηκαν. Πιο συγκεκριμένα στο τρίτο κεφάλαιο παρουσιάζονται τα πειραματικά αποτελέσματα που προέκυψαν από τη μελέτη νανοσωματιδίων οξειδίων του σιδήρου καλυμμένων με πολυμερή αλλά και ακάλυπτων όταν διεγείρονταν με παλμούς laser χρονικής διάρκειας 35 ps και 4 ns και μήκη κύματος 532 nm και 1064 nm. Στόχος της μελέτης ήταν ο προσδιορισμός αν το πολυμερές που βρίσκεται αγκυροβολημένο στην επιφάνεια του νανοσωματιδίου ή απουσία αυτού έχει κάποια επίδραση στις μη-γραμμικές οπτικές ιδιότητες αυτών. Στο τέταρτο κεφάλαιο παρουσιάζονται τα πειραματικά αποτελέσματα της μελέτης των μικκυλιακών συστημάτων Pd για μήκη κύματος διέγερση 532 nm και 1064 nm. Η μελέτη έγινε για χρονικό εύρος παλμού laser 35 ps και 4 ns. Τα συμπολυμερή τα οποία σχημάτιζαν το μικκύλιο απέτρεπαν τη συσσωμάτωση των νανοσωματιδίων Pd και τη δημιουργία σταθερών κολλοειδών διαλυμάτων. Τα συμπολυμερή που χρησιμοποιήθηκαν επίσης δημιουργούσαν νανοδομές οι οποίες είχαν καλά ορισμένες διαστάσεις και σχήματα. Στόχος της μελέτης ήταν να διαπιστωθεί το κατά πόσο η διάσταση, το σχήμα καθώς και η αλλαγή του συμπολυμερούς επηρεάζουν τις μη-γραμμικές οπτικές των νανοδομών. Στο πέμπτο κεφάλαιο παρουσιάζονται τα αποτελέσματα που προέκυψαν από τη μελέτη οργανομεταλλικών ενώσεων διθειολενικών συμπλόκων. Η επίδραση των υποκαταστών του σκελετού του μορίου καθώς και του κεντρικού ατόμου της ένωσης εξετάστηκαν για παλμούς laser χρονικής διάρκειας 35 ps και μήκους κύματος 532 nm και 1064 nm. Στο έκτο και τελευταίο κεφάλαιο παρουσιάζονται τα πειραματικά αποτελέσματα που προέκυψαν από τη μελέτη δυαδικών συστημάτων φουλλερενίων δότη-αποδέκτη ηλεκτρονίων για παλμούς laser 35 ps και μήκους κύματος 532 nm. Τα αποτελέσματα δείχνουν ότι αυτά τα συστήματα έχουν πολύ αυξημένες μη-γραμμικές οπτικές σε σχέση με τα απλά φουλλερένια καθιστώντας τα υποψήφια για πιθανές εφαρμογές σε διατάξεις οπτικών αισθητήρων και οπτικών πυλών. / The field of optics that examines the interaction of matter with very high intensity radiation is called nonlinear optics. When a material is exposed to radiation with high intensity such as the radiation emitted by a laser, the optical properties of the material change as a result of the induced polarization that occurs in the atoms or the molecules that constitute the material. This in turn can lead to a variety of phenomena that helps us to understand and establish relations between the structure and the physical mechanisms that take place when light interacts with matter. Materials with large nonlinear optical properties are considered possible candidates for applications in a wide range of technology such us optical or quantum computers or even in the field of telecommunications. In this work the nonlinear optical properties of metallic nanoparticles, organometallic molecules and fullerene derivates is examined. The investigated systems were in form of solutions and the nonlinear optical properties were determined with the use of Z-scan and OKE techniques. The laser pulse duration was 35 ps and 4 ns, while the excitation wavelength was 532 nm and 1064 nm respectively. In the first chapter an introduction is presented to some elements of the field of nonlinear optics. Then the derivation of the relations that describe the nonlinear optical parameters like the third order susceptibility (χ(3)) with the use of electromagnetic theory and quantum mechanics is presented. At the end some interesting phenomena that occur as a result of third order susceptibility are described. The second chapter is devoted to the experimental techniques that were used to determine the nonlinear optical properties of the investigated systems that are presented in this work. The Z-scan and OKE techniques are described thoroughly as well and the process of the determination of the nonlinear optical properties from the experimental data. In the next four chapters, experimental results are presented of the nonlinear optical properties for all the systems that were studied during this work. At the third chapter the results for γ-Fe2O3 nanoparticles are presented. Those systems were either covered or uncovered with polymeric brushes, and had different sizes of the nanoparticle core. The results show that the presence or not of the polymeric brushes, as well and the size of the core has an impact on the nonlinear optical properties those systems. In chapter four are presented the results from the investigation of the nonlinear optical properties of Pd nanoparticles encapsulated into amphiphilic block copolymer micelles. The investigation was done under 35 ps and 4 ns laser pulse duration at excitation wavelengths of 532 and 1064 nm. It is concluded that the NLO response of the systems is depending on the size of the micelle, the shape but also from the metallic load of the micelle. In the final two chapters they are presented the results regarding the NLO properties of organometallic and fullerene derivates molecules. In chapter five the investigation of the nonlinear optical properties of various dithiolene complexes is presented, under 35 ps laser pulse duration at 532 and 1064 nm. The results shows that the central atom attached to the molecule is playing crucial role to the NLO response but also and the number and the nature of substituent attached to the molecule. At the final chapter the determined NLO properties of some donor – acceptor fullerene derivatives are presented. The results show that functionalized fullerene derivatives have greater NLO response than the neat fullerene making them promising candidates for applications in optoelectronics and all-optical switching.

Cette thèse présente un travail relatif à l'étude de la structure en spin longitudinal du nucléon. Le but est de déterminer la contribution des constituants du proton, quarks et gluons, à la formation de son spin 1/2. L'analyse s'appuie sur les données de l'expérience COMPASS qui bénéficie d'un faisceau de muons polarisés à 200 GeV diffusé sur les protons polarisés d'une cible d'ammoniac (NH₃) de 1,2 m de long. On mesure l'asymétrie de spin longitudinal des sections efficaces de diffusion profondément inélastique. On extrait la fonction de structure en spin du proton, g₁p, étendant la couverture cinématique mondiale à des régions inexplorées jusqu'à maintenant (0,0036 < x < 0,57; 1,03 < Q² (GeV/c)² < 96 et 23 < W² (GeV/c)² < 320). Les résultats, d'une grande précision statistique, sont inclus dans une analyse des données mondiales de g₁p, g₁d et g₁n (proton, deutéron et neutron) au 2ème ordre de QCD afin de paramétrer les distributions de quarks et de gluons polarisés. L'étendue de la couverture cinématique en x et Q² des données mondiales de g₁, un élément déterminant pour la sensibilité à la polarisation des gluons ΔG, s'avère trop limitée pour constituer une extraction précise de celle-Ci. Néanmoins, l'analyse QCD permet de déterminer la contribution du spin des quarks au spin du proton à 0.26<ΔΣ<0.33 à Q² = 3 (GeV/c)² dans le schéma MSbar. L'étude montre que l'incertitude principale sur ΔΣ est liée au choix des formes fonctionnelles utilisées dans la régression des données. Enfin, la règle de somme de Bjorken, qui constitue un test de QCD, est vérifiée avec une précision de 9% en utilisant les données de COMPASS uniquement. / The work presented in this thesis is related to the study of the longitudinal spin structure of the nucleon. The aim is to determine the contribution to the spin 1/2 of the proton in terms of its constituents, quarks and gluons. The analysis is performed on the data taken with the COMPASS experiment, which benefits from a polarised muon beam at 200 GeV scattered off polarised protons from an ammonia target of 1.2 m long. The double longitudinal spin asymmetry of deep inelastic scattering cross-Section. The spin-Dependent structure function of the proton g₁p is derived from these measurements, which extend the kinematic world coverage to unexplored region so far (0,0036 < x< 0,57; 1,03 < Q² (GeV/c)² < 96 and 23 < W² (GeV/c)² < 320).The results obtained with a high statistical precision are included in a Next-To-Leading order QCD analysis of world g₁p, g₁d and g₁n (proton, deuteron and neutron) data to parametrise the polarised quark and gluon distributions. The g₁ world coverage of the x and Q² kinematic domain, which is a key point in the sensitivity to the gluon polarisation ΔG, turns out to be too limited for an accurate ΔG determination. Nevertheless, the QCD analysis allows to determine the quark spin contributions to the proton spin to 0.26<ΔΣ<0.33 at Q² = 3 (GeV/c)² in the MSbar scheme. The dominant uncertainty on ΔΣ is related to the choice of functional forms assumed in the fit. Finally, the Bjorken sum rule, which constitutes a fundamental test of QCD, is verified on the COMPASS data alone with a precision of 9%.