Spectroscopic measurements are detailed within this thesis, utilising incoherent neutron scattering to examine the dynamics of various condensed-matter systems, from nanosecond to sub-femtosecond timescales. The body of this work is divided into two distinct areas of research. I. Nuclear Momentum Measurements of Multiple Masses Deep inelastic neutron scattering (DINS) is used to probe the nuclear momentum distributions and kinetic energies of individual atomic species in sodium hydride (both in bulk and as nanoparticulates within a silica matrix), enriched lithium-7 fluoride and lithium tetra-ammoniate. Extension of DINS to examine heavier (M>4amu) nuclei is detailed, accomplished by the application of a simple stoichiometric fixing technique within the standard DINS theory and analysis protocols. The validity and accuracy of such simultaneous measurements are discussed. II. The Dynamics of Coordinated Ammonia in Zeolite A Inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) are utilised in the examination of vibrational and stochastic dynamics of the ammonia molecule, as coordinated to the internal surface of a zeolite host. Both sodium and copper-exchanged forms of zeolite-A are studied, with proton-weighted, low energy phonon-modes and rotational processes being observed and assigned.

This thesis presents applications of near infrared diode lasers to high resolution spectroscopy of transient radical species. Firstly, time resolved near infrared laser gain versus absorption is utilised in Chapter 2 to determine the I∗ quantum yield following ultraviolet photolysis of iodobenzene and its fluorinated analogues. The experimental method is first confirmed by comparison with literature values of the quantum yield for iodomethane photolysis, returning a quantum yield of Φ(I∗) = 0.71 ± 0.04 in good agreement with the literature, before being applied to determine the I∗ quantum yield following 248 nm and 266 nm photolysis of iodobenzene (Φ(I^∗) = 0.28 ± 0.04) and pentafluoroiodobenzene (Φ(I^∗) = 0.32 ± 0.05). The I^∗ quantum yields for 4-fluoroiodobenzene, 2,4-difluoroiodobenzene and 3,5-difluoroiodobenzene are also reported in order to determine the effect of selective fluorination on the dynamics of the photodissociation process. This work complements velocity-map ion imaging studies and spin-orbit resolved ab initio calculations of the ultraviolet photolysis of these compounds. Chapter 3 details the development of a narrow-bandwidth tunable continuous wave ultraviolet radiation source, through sum frequency mixing of tunable near infrared diode lasers with a fixed frequency, high powered, solid state laser. The application of the UV radiation source to spectroscopy of the A¹A₂ − X¹A₁ electronic band of formaldehyde is explored, where absolute absorption cross sections are determined for rotational transitions within the 220410 and 220430 vibronic bands. The sub-Doppler resolution has allowed refinement of the rotational constants for the slowly predissociating excited state of the 2²₀4³₀ vibronic band. The lifetimes of several rotational levels is determined to be in the range 0.74 ns to 1.46 ns. In Chapter 4 the UV radiation source developed in Chapter 3 is applied to the A ²Σ⁺ − X ²Π electronic band of the OH radical. Firstly, this source is utilised to probe a continuous supply of hydroxyl radicals using cavity-enhanced absorption spectroscopy and wavelength modulation spectroscopy. Pressure induced broadening parameters for the Q₁(2) rotational transition for He, Ne, Ar and N₂ buffer gases are also measured. Following the successful application of this source to probe a continuous OH source at atmospheric pressure, the UV spectrometer is used to probe OH radicals from nitric acid photolysis at 193 nm, where the nascent speed distribution and Doppler lineshape is shown to be in excellent agreement with the literature. Time resolved absorption spectroscopy of the nascent OH fragment also returns a translational relaxation constant of k_trans = (3.85±1.06)×10⁻¹⁰cm³molecule⁻¹s⁻¹, which is in good agreement with literature values. These preliminary results indicate the potential of this narrow-bandwidth tunable UV source as an absorption-spectroscopy-based probe of nascent Doppler profiles. Chapter 5 presents the application of frequency-modulated radiation from a near infrared diode laser as a probe of the angular momentum polarisation of the nascent CN fragments, produced by 266 nm photolysis of ICN. These CN fragments are probed in the high rotational states of both the ground and first excited vibrational level on the A ²Π − X ²Σ⁺ electronic transition; in particular these constitute the first measurements of alignment and orientation in the first excited vibrational level at this photolysis wavelength. The alignment parameters reported for both vibrational levels are comparable, indicating that the incoherent dynamics contributing to their formation are the same. In contrast, the orientation of the v = 1 CN fragment is shown to be of opposite sign to that of v = 0 at this photolysis wavelength, although the absolute differences in their orientation parameters are similar to that observed for photolysis at 248 nm. This observation is consistent with coherent orientation arising from phase differences between wavepackets propagating on multiple excited potential energy surfaces.

Quantum information processing (QIP), which inherently utilizes quantum mechanical phenomena to perform information processing, may outperform its classical counterpart at certain tasks. As one of the physical implementations of QIP, the electron-spin based architecture has recently attracted great interests. Endohedral fullerenes with unpaired electrons, such as N@C₆₀, are promising candidates to embody the qubits because of their long spin decoherence time. This thesis addresses several fundamental aspects of the strategy of engineering the N@C₆₀ molecules for applications in QIP. Chemical functionalization of N@C₆₀ is investigated and several different derivatives of N@C₆₀ are synthesized. These N@C₆₀ derivatives exhibit different stability when they are exposed to ambient light in a degassed solution. The cyclopropane derivative of N@C60 shows comparable stability to pristine N@C₆₀, whereas the pyrrolidine derivatives demonstrate much lower stability. To elucidate the effect of the functional groups on the stability, an escape mechanism of the encapsulated nitrogen atom is proposed based on DFT calculations. The escape of nitrogen is facilitated by a 6-membered ring formed in the decomposition of the pyrrolidine derivatives of N@C₆₀. In contrast, the 4-membered ring formed in the cyclopropane derivative of N@C₆₀ prohibits such an escape through the addends. Two N@C₆₀-porphyrin dyads are synthesized. The dyad with free base porphyrin exhibits typical zero-field splitting (ZFS) features due to functionalization in the solid-state electron spin resonance (ESR) spectrum. However, the nitrogen ESR signal in the second dyad of N@C₆₀ and copper porphyrin is completely suppressed at a wide range of sample concentrations. The dipolar coupling between the copper spin and the nitrogen spins is calculated to be 27.0 MHz. To prove the presence of the encapsulated nitrogen atom in the second dyad, demetallation of the copper porphyrin moiety is carried out. The recovery of approximately 82% of the signal intensity confirms that the dipolar coupling suppresses the ESR signal of N@C₆₀. To prepare ordered structure of N@C₆₀, the nematic matrix MBBA is employed to align the pyrrolidine derivatives of N@C₆₀. Orientations of these derivatives are investigated through simulation of their ESR spectra. The derivatives with a –CH3 or phenyl group derived straightforward from the N-substituent of the pyrrolidine ring are preferentially oriented based on their powder-like ESR spectra in the MBBA matrix. An angle of about is also found between the directors of fullerene derivatives and MBBA. In contrast, the derivatives with a –CH₂ group inserted between the phenyl group and the pyrrolidine ring are nearly randomly distributed in MBBA. These results illustrate the applicability of liquid crystal as a matrix to align N@C₆₀ derivatives for QIP applications.

Herein, the influence of protonation and adsorption upon the redox and electrocatalysis of quinone species - specifically anthraquinone derivatives – is investigated. Through the comparison of the measured rate constants of one-electron reductions of a family of quinones in acetonitrile at both graphite and gold electrodes, it was confirmed that the redox potential indirectly influences the rate of electron transfer in a manner consistent with the potential-dependence of the density of states. In aqueous media, the voltammetric response of both anthraquione-2-sulfonate (AQMS) and anthraquinone-2,6-disulfonate (AQDS) was measured over the full aqueous pH range. A model is provided which is able to describe not just the variation in the formal potential but also the peak height as a function of pH. Importantly, this model predicts that the formal potential for the first (Ef1) and second (Ef2) electron transfers are comparable in magnitude (E^θ _f2−E^_θf1 equals -15mV for AQMS and -36mV for AQDS). This quantitative model is then further extended to consider the situation in which the system is not fully buffered, giving insight into the change of pH at the electrode surface during experimentation. Adsorption to graphitic electrodes can impart a strong influence on the measured voltammetric response. It is demonstrated that through the pre-exposure of a newly prepared graphitic electrode to organic solvents, these adsorption processes can be predominantly blocked. Moreover, it is shown that the electroactivity of the electrode is not significantly altered. This thesis also highlights two cases in which adsorption of the electroactive species may be used to positive effect. First, the surface adsorption of anthraquinone-2-monosulfonate is studied on a graphite electrode, where it is demonstrated that the heterogeneity of the electrode surface may be probed through studying the electrochemical response of the adsorbed species. From this work it is concluded that the rate of electron transfer at the graphitic basal plane is 2-3 orders of magnitude lower than that observed on the edge plane sites. Second, the co-adsorption of DNA and anthraquinone-2-monosulfonate is used as an indirect method to measure the solution phase concentration of DNA (LOD = 8.8μM). The reduced form of anthraquinone is also known to readily reduce oxygen. Through the use of a boron-doped diamond electrode it was possible to directly study the anthraquinone mediated reduction mechanism. Significantly, the voltammetric response indicates the reduction of the oxygen via the semi-quinone intermediate (kf = 4.8 × 10⁹ mol⁻¹ dm³ s⁻¹) is over two orders of magnitude faster than the reaction involving the di-reduced form (kf = 1 × 10⁷ mol⁻¹ dm³ s⁻¹). More importantly, this work provides voltammetric evidence for the existence of the semi-quinone species. This work is subsequently extended through the investigation of the poorly soluble anthraquinone derivative quinizarin. Not only is it possible to detect voltammetrically this biologically relevant species to concentrations as low as 5nM (100ppt), but the methodology also allows the electrochemistry of the quinizarin species to be probed, something which was not previously possible.

In this work, we wish to determine the free energy landscape and the nucleation rate associated with the process of homogeneous ice nucleation. To do this, we simulate the homogeneous nucleation of ice with the mW monatomic model of water and with all-atom models of water using primarily the umbrella sampling rare event method. We find that the use of the mW model of water, which has simpler dynamics compared to all-atom models of water, but is nevertheless surprisingly good at reproducing experimental data, results in very reasonable agreement with classical nucleation theory, in contrast to some previous simulations of homogeneous ice nucleation. We suggest that previous simulations did not observe the lowest free energy pathway in order parameter space because of their use of global order parameters, leading to a deviation from classical nucleation theory predictions. Whilst monatomic water can nucleate reasonably quickly, all-atom models of water are considerably more difficult to simulate, primarily because of their slow dynamics of ice growth and the fact that standard order parameters do not work well in driving nucleation when such models are being used. In this thesis, we describe a local, rotationally invariant order parameter that is capable of growing ice homogeneously in a biassed simulation without the unnatural effects introduced by global order parameters, and without leading to non-physical chain-like growth of 'ice' clusters that results from a naïve implementation of the standard Steinhardt-Ten Wolde order parameter. We have successfully used this order parameter to force the growth of ice clusters in simulations of all-atom models of water. However, although ice growth can be achieved, equilibrating simulations with all-atom models of water is extremely difficult. We describe several approaches to speeding up the equilibration in all-atom models of water to enable the computation of free energy profiles for homogeneous ice nucleation.

Chapter1 gives an overview of the basic principles of electrochemistry. A rigorous electrochemical study on the solution phase and solid phase cobalt phthalocyanine (CoPC) is presented in chapter2. The formof CoPC on carbon electrodes was characterized by scanning electron microscope (SEM). The use of CoPC modified edge plane pyrolytic graphite (CoPC-EPPG) for sensing nitrite (NO₂⁻) was also investigated. It was found that the claimed mediator CoPC has no influence on the process. A bare glassy carbon (GC) electrode was successfully applied for the quantitative determination of nitrite as a simple alternative to the modified electrodes reported in the literature (chapter3). Chapter4 compares the voltammetric responses of an edge plane pyrolytic graphite electrode covalently modifed with 2-anthraquinonyl groups (EPPG-AQ2) and solution phase anthraquinone monosulphonate (AQMS) in the presence of a limited concentration of protons. The solution phase and surface bound species show analogous responses resulting in split waves. Digisim™ simulation of the AQMS voltammetry have shown that the pH adjacent to the electrode may be altered by up to 5-6 pH units in low buffered solutions; this is caused by the consumption of protons during the electrochemical reaction. Chapters5 and 6 compare the electrochemical properties of 2-anthraquinonyl groups covalently attached to an edge plane pyrolytic graphite (EPPG) and to a gold electrode. In both cases simulations using newly developedMarcus-Hush-Chidsey theory for a 2e⁻ process assuming a uniform surface did not achieve a good agreement between theory and experiment. Subsequently two models of surface inhomogeneity were investigated: a distribution of formal potentials, E^Ө, and a distribution of electron tunneling distances, r₀. For both EPPG-AQ2 and Au-AQ2 modified electrodes the simulation involving E^Ө distribution turned out to be the most adequate. This is the first time that Marcus-Hush-Chidsey theory has been applied to a 2e⁻ system. Chapter7 briefly summarizes the obtained results.

Nuclear magnetic resonance (NMR) is a popular spectroscopic method and has widespread use in many fields. Recent developments in solid-state NMR have increased interest in experiment and, alongside simultaneous developments in computational theory, have led to the field dubbed 'NMR crystallography.' This is a suite of methodologies, complementing the capabilities of other crystallographic methods in the determination of atomic structure, especially when large crystals cannot be made and when exploring materials with phenomena such as compositional, positional and dynamic disorder. NMR J-coupling is the indirect coupling between nuclear spins, which, when measured, can reveal a wealth of information about structure and bonding. This thesis develops and applies the method of Joyce for the prediction of NMR J-coupling in condensed matter systems using plane-wave pseudopotential density-functional theory, an important requirement for efficient treatment of finite and infinite periodic systems. It describes the first-ever method for the use of ultrasoft pseudopotentials and inclusion of special relativistic effects in J-coupling prediction, allowing for the treatment of a wider range of materials systems and overall greater user friendliness, thus making the method more accessible and attractive to the wider scientific community.

This thesis describes the development of a new experimental technique for studying tunable-collision-energy, quantum state-selected, low-temperature ion-molecule reactions. This has been achieved through the combination of a Stark decelerator for neutral dipolar molecules, and a linear Paul ion trap. The Stark deceleration process for ND₃ was examined in detail, through the analysis of experimental data in combination with newly written molecular dynamics simulation programs. In order to prepare a sample of molecules appropriate for collision studies, additional beamline components were introduced after the decelerator. These components were: two hexapoles, to provide transverse focussing, maximising the molecular density; a molecular buncher, providing increased longitudinal velocity resolution; and a fast-opening shutter, to separate decelerated molecules from undecelerated molecules. The sympathetic-cooling of Xe⁺ ions and ND⁺₃ ions by laser-cooled, Coulomb crystallised ⁴⁰Ca⁺ ions with the ion trap was also studied. In particular, the stable trapping of Xe⁺ was demonstrated for the first time, and the experimental developments that led to this are discussed. The work in this thesis represents significant progress towards studying the reaction of tunable-energy ND₃ in the |j,mk> = |1,−1> quantum state with cold Xe⁺ ions. Ion-molecule reactions utilising ND₃ molecules electrostatically guided through the Stark decelerator were performed. It was observed that the main source of error in these experiments was in the calculation of the initial number of Xe⁺ ions that had been sympathetically cooled into the Coulomb crystal. The sensitivity of the crystal morphology to the number of Xe⁺ ions was evaluated using molecular dynamics simulations. Strategies have been developed to reduce this uncertainty in future studies. In addition to experimental work, the theory of low temperature ion-molecule reactions has been developed further. The temperature at which classical and quantum mechanical calculations diverge due to purely statistical effects has been investigated using different model intermolecular potentials, for closed-shell and open-shell species, and in the ground and rotationally excited states. From the results of these calculations, several promising candidate reactions have been suggested that might exhibit statistical quantum behaviour at experimentally achievable temperatures.

Flavour Tagging at the LHCb experiment is a fundamental tool for the measurement of B oscillations and the study of CP violation. This document explains the development of different tagging techniques and the different strategies used to combine them to determine the flavour of the B meson as precisely as possible. The response of the tagging algorithms also needs to be optimized and calibrated. Both procedures are described using the available LHCb datasets corresponding to various integrated luminosities. First results on the tagging performances are shown for different control channels and physics measurements.

This thesis deals with the investigation of the first hyperpolarizabilities (β) of a large number of molecules linked to other molecules either covalently or noncovalently. Chapter 1 gives a brief introduction to supramolecular chemistry and Nonlinear Optics (NLO). A survey of literature pertinent to noncovalently interacting supramolecular assembly and their NLO properties as well as NLO properties of oligomeric systems has been presented. The scope of the present investigation has been described at the end of the chapter. Chapter 2 discusses all the methods used in carrying out this thesis work. The first hyperpolarizabilities (β) of all the compounds have been measured by the hyper Rayleigh scattering (HRS) technique; the experimental details of which are written in this chapter. Various spectroscopic techniques such as NMR, IR, UV-Vis, etc. that were used in the investigation have been presented. The subsequent chapters 3-5 deal with the actual results obtained in this work. In chapter 3 first hyperpolarizabilities of o-, m-, and p-aminobenzoic acids and their oligomers viz., dimer, trimer and tetramer (covalently linked) have been studied. The compounds are synthesized and characterized by various spectroscopic methods and their β values have been measured by HRS. The hyperpolarizability increases in going from the monomer to the dimer but decreases subsequently from the dimer to the trimer to the tetramer. This unexpected trend in β has been attributed to the formation of molecular aggregates in the trimers and tetramers. Further evidences of aggregation come from the results of1H NMR spectroscopy and conductivity measurements. In chapter 4, synthesis, characterization and HRS investigation to probe the formation, dissociation and binding constants of hydrogen bonded supramolecular complexes (noncovalent interaction) formed in solution between 6-amino-2-(pivaloylamino)pyridine and ferrocene functionalized barbituric acid and 5-methoxy-N,N′-bis(6-amino-2-pyridinyl)-1,3-benzenedicarboxamide and ferrocenyl barbituric acid have been described. From the HRS data the stoichiometry of the supramolecular complexes has been determined and compared to that from the NMR data. Some of the complex stoichiometries that are measured by HRS have not been seen in the NMR data and vice versa. The results have been rationalized in terms of the strengths and weaknesses of various spectroscopic methods as applied to this problem. Many fold increase in the β value has been realized in the supramolecular complex formation process. Depolarized HRS experiments have been carried out to obtain structural information on the complexes. In the last chapter the synthesis, characterization and measurements on the first hyperpolarizabilities of unsubstituted tetraphenylporphyrin and its metallated complexes have been presented. Synthesis of supramolecular complexes of ferrocenyl barbituric acid with functionalized porphyrin compounds has been carried out although the amount of the final complex was insufficient for HRS measurements. This chapter ends with a perspective for the future work in the direction.