This thesis is an account of an experiment performed at the CERN proton synchrotron. More than 2,600 reactions of the type π— + p → K° + K̄° + n and 130 of the type π— + p → ∧ + ∧- + n were detected in a magnet spark chamber. The apparatus and its performance are described. Problems specifically related to the automatic measurement of spark chamber photographs, and their geometrical and kinematic analysis, are discussed. Emphasis is placed on the physical interpretation of the K°1 K°1 n final state; in particular on the peripheral production and decay correlations of the S*, fₒ, A2 and f' mesons. From a study of the ∧∧- system in ∧∧-n final states there is no evidence to indicate the production of a heavy boson.

A general introduction is given to the problem of the stability of two-dimensional, symmetric, nearly-parallel flow of a viscous, incompressible fluid in a channel with fixed walls. The method of matched asymptotic expansions is introduced, and the Lin-Heisenberg methods are discussed in the light of this method. Curves of neutral stability are calculated in the (Rk)-plane (where R is the Reynolds number of the basic flow and k is the wave number of a disturbance), by Thomas' (1953) finite-difference method applied to the Orr-Sommerfeld problem, for the case of flow in a slightly divergent channel. A study is made of asymptotic approximations (for kR → 00) of certain clearly-defined solutions of the Orr-Sommerfeld equation, using the method of matched asymptotic expansions and composite series. This theory is applied to the asymptotic equations of the neutral curves.

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In recent years many calculations of arrays of Franck-Condon factors have been made and some of these have been checked by intensity measurements under a very limited range of conditions. This thesis describes some experiments in which the intensity of the bands of the nitrogen second positive system was measured. The system was excited by a discharge through very low temperatures low pressure, mixtures of helium and nitrogen, for a large range of helium pressures. The object of this work was to measure the intensity distribution in the system when it was excited under a known range of conditions to obtain results which could be compared with aurroral observations and to investigate whether the theoretical assumptions which form the background to the calculations of the q values are valid over this range of conditions. The electronic transition moment was calculated for a number of conditions and the reliability of the q values was assessed. It was found that while the majority of the q values were reliable at low helium pressures some became less reliable at high helium pressures, the electronic transition moment was also shown to vary with helium pressure. It was concluded that the theory is valid to a first approximation for low gas pressures only. The results were also used to try to gain an insight into the excitation processes occuring and their relative importance. Intensity measurements were made on some bands of the first negative system In recent years many calculations of arrays of Franck-Condon factors have been made and some of these have been checked by intensity measurements under a very limited range of conditions. This thesis describes some experiments in which the intensity of the bands of the nitrogen second positive system was measured. The system was excited by a discharge through very low temperatures low pressure, mixtures of helium and nitrogen, for a large range of helium pressures. The object of this work was to measure the intensity distribution in the system when it was excited under a known range of conditions to obtain results which could be compared with aurroral observations and to investigate whether the theoretical assumptions which form the background to the calculations of the q values are valid over this range of conditions. The electronic transition moment was calculated for a number of conditions and the reliability of the q values was assessed. It was found that while the majority of the q values were reliable at low helium pressures some became less reliable at high helium pressures, the electronic transition moment was also shown to vary with helium pressure. It was concluded that the theory is valid to a first approximation for low gas pressures only. The results were also used to try to gain an insight into the excitation processes occuring and their relative importance. Intensity measurements were made on some bands of the first negative system

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No description available.

After Feynman's proposal, in 1982, to simulate quantum systems using quantum computers, much effort has been focused on the study and realisation of machines capable of harnessing the power of quantum mechanics for simulation and computation. Many difFerent implementations have been proposed for the realisation of quantum technologies, all with their advantages and disadvantages. Integrated silicon photonics recently emerged as a promising approach: in fact all the necessary components for quantum computation can be integrated together on a silicon chip. In addition, the information carriers (photons) have very long coherence times and can be manipulated in an intrinsically phase-stable manner. The realisation of quantum photonic technologies is tied to the existence of a high efficiency single photon source (ideally on-demand). One of the possible solutions is in the multiplexing of many probabilistic photon pair sources. In this thesis we present four different quantum photonics experiments. We show the integration in a silicon quantum photonics platform of fundamental components for the implementation of any quantum information processing. We show that with our approach we can obtain high fidelity quantum states and high levels of entanglement. Furthermore, we also demonstrate the implementation of a hybrid (time and space) multiplexed single photon source in bulk optics.

This thesis provides an important basis for understanding the surface modulation mechanism and electronic structure variation on semiconducting surfaces and metallic thin films. The use of real-time photoelectron spectroscopy (REES) makes it possible to monitor the solid surfaces during in situ processing. The surfaces that have been investigated were (100) facet boron-doped diamond surfaces and iron thin films. The surface processing treatments include annealing, thin film coating and exposure to oxygen and hydrogen microwave plasma sources. The oxygen-terminated (100) facet diamond was annealed up to 1000°C while monitoring with REES. The oxygen desorption process on the surface can be divided into four distinct stages according the oxygen concentration on the diamond (100) surface during the heating cycle. The ratio of ketone/ether groups has been investigated. Moreover, the true band bending on O-terminated (100) has been investigated with real-time characterization, which has a maximum difference of +1.0 eV comparing with the room temperature XPS spectra data. Fluorouracil (5-FU), as a drug widely used in leukaemia and bowel cancer treatment, which is demonstrated to degrade on silver coated catheter surfaces, producing hydrofluoric acid and therefor leading to adverse effects on patients. In order to compare diamond as coating material, the adsorption of 5-FU on the oxygen and hydrogen terminated diamond (100) surfaces has been studied with x-ray photoelectron spectroscopy (XPS), showing extremely different behaviours. Utilising the shape memory alloy (SMA) substrate, the continuously mediated strain was transferred from the substrate to Fe films through a thermally controlled shape memory effect. The pure strain modulated electronic structure in the Fe thin films was studied using in situ XPS and first-principle calculations. The result demonstrates that the compressive strain increases the overlap of outer orbits and enhances the shielding effect to core electrons, resulting in significant tunability on the binding energy of core electrons and related magnetic anisotropy.

With modern high performance calculation, computer simulation provides us with a possible way to analyse and visualize the atoms and molecules of materials within nanometre scale and picoseconds which can not be simply achieved in real-life experiments. Therefore it is a great tool to study the nano-structure formation of materials including crystals as well as glasses. In this thesis, alumino-silicates including nepheline and its compositional variations have been studied. Melts of them have been simulated and glasses have been derived by melt-quenching procedures. Static structures and dynamic properties have been studied. Specifically, the distribution of mobile metallic ions, which fundamentally affects the properties of glasses, has been simulated in this study to give a better understanding of the roles mobile ions play. In particular, we are interested in whether micro-segregation of metallic ions occurs as it does in silicates [1]. Molecular dynamics simulations of alumino-silicates nepheline (KXNa4−XAl4Si4O16) have been performed to obtain first the structure of molten nepheline. Five different alkali ratios have been taken to explore the effect of ionic radius and field strength on segregation. Radial Distribution functions, REDOR second moments, Vibrational Densities of States and molecular structure snapshots reveal how alkali ions distribute non-randomly, form channels in between the framework atoms of both molten and glassy nepheline. This nanostructure of nepheline at Tg=1200K is virtually the same as the quenched structure at room temperature, confirmed by the snapshots. When K+ replaces Na+ in the system, it occupies more volume. Both melt viscosity and boson peak intensity in quenched glass showed dramatic increasing due to the percolation channels affected by K+ concentration. To replicate the dynamics properties of melts, three series of molecular dynamics simulations with varied alumino-silicate composition, each containing different ratios of Al/Si, have been performed including nepheline for which Al/Si = 1. Mean square displacements have been calculated from trajectories at 2000K to derive diffusion constant. The Einstein-Stokes equation and the Eyring equation were then used to derive the viscosity and compared. The Eyring results show a better replication of a fitted Adam-Gibbs model with measured viscosity values.