I give a review of the theory of the hydrogen molecular ion H2+ and its isotopomers D2+ and HD+ including the direct analytical solution and the standard adiabatic approximation. I discuss dissociation limits for homonuclear and heteronuclear species; the effect of an external electric field; non adiabatic calculations, relativistic and radiative effects; and spectroscopic measurements of H2+ and D2+ with a comparison of theoretical to experimental values. I give a detailed description of the fast ion-beam spectrometer as used for both laser-beam and microwave spectroscopy and describe the challenges involved in making high resolution spectroscopic measurements. An account is given of theory, experimental details and measurements of transition frequencies and intensities of the forbidden rotational transition (v = 19, N = 1) - (v = 19, N = 0) in the ground electronic state (X2Σg+, also represented as 1sσg) of H2+. Theory has predicted that the transition has measurable intensity due to the Fermi contact hyperfine interaction causing a breaking of electronic g/u symmetry resulting in the mixing of ortho-para states. The measurements were made in both single and double resonance using a fast ion beam/microwave spectrometer at a transition frequency of 14961.7 ± 1.1 MHz, in agreement with the theoretical prediction of 14960 ± 3 MHz. An account is also given of a further search that was conducted for a second forbidden rotational transition (v = 0, N = 1) - (v = 0, N = 0) in the first excited electronic state (2pσu) of H2+. A discussion is given on the possibility of making further observations of forbidden rotational transitions and the experimental difficulties involved; and of adapting the experimental techniques used in order to observe the recently discovered (v = 1, N = 0) in the first excited electronic state (2pσu) of H2+.

This thesis comprehensively describes the computational design, fabrication and characterisation of multilayer mirrors intended as key reflective elements for the X-ray and extreme ultraviolet radiation ranges. The first central theme was to present various designs for the requirements of soft X-ray microprobes, EUVL lithography systems and high harmonic generation sources, i.e. monochromator, broad-angle supermirror, broadband intensity and polarising beamsplitters and order-selecting mirror. The particle swarm optimisation method was successfully applied in a global search of materials for the structure of mirrors. The robust designs made possible are considered to alleviate fabrication difficulties, such as control of layer thickness errors. The second important theme was to analyse the interfacial and surface imperfections in multilayer mirrors. This work is crucial in improving the fabrication technology and in : understanding the basic growth status at the interfaces. Transmission electron microscopy, X-ray diffraction and atomic force microscopy were used in these experiments. The analyses are based on innovative methods, namely time series analysis and wavelet analysis. The evolution tendencies of the layer thicknesses, interfacial roughness and interdiffusion were determined, as were correlated growth, structural uniformity, surface stress damage and surface roughness. The final theme was to test a multilayer monochromator for use in a soft X-ray microprobe for radiobiological studies on pathological cells and tissue. The source spectrum was determined using different incidence angles on multilayer mirrors and some suggestions for improvement were presented.

Owing to the current security climate, there is growing demand for systems capable of detecting controlled substances, such as explosives, incendiaries and solvents in closed container in-situ and noninvasively. Previously, bottles would need to be opened and sampled to determine the contents but in recent years non-invasive systems have been developed. These are typically large stand-alone or bench top devices that have been developed primarily for airport security. These screening systems generally work on principles adapted from other techniques not specific to this purpose. With this in mind, a highly sensitive, novel technique that lends itself to a hand held device that would allow for greater flexibility in its use, has been devised and is presented here. The system comprises two small flexible antenna that wrap around the bottle and excite the contained sample electromagnetically such that it resonates. This resonance is dependant on both the shape of the bottle and the permittivity of the contained liquid. It has been shown to a reasonable certainty that the contribution to the resonant response of the sample from the geometric shape of the bottle and the permittivity of the liquid are independent. With adequate knowledge of the bottle shape, it follows that with this and the resonant response of the sample, the permittivity of the liquid can be determined and the liquid classified. The work is presented as a foundation on which a classification system might be developed rat her than a working classification system. A screening system must be capable of identifying not non-aqueous liquids such as incendiaries or solvents but also aqueous liquids such as alcoholic beverages and hydrogen peroxide from water. As such, the work has also focused on the detectability of hydrogen peroxide, which is both a precursor to or a constituent of a number of improvised explosives, and is very similar to water dielectrically .

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No description available.

Thin films of organic semiconducting materials, such as copper phthalocyanine (CuPc) and C60, can be used in photovoltaic devices. The interface between these materials is the site of exciton dissociation, and thus a key region of interest in their study. The processes that occur within these films and at interfaces are governed by the local morphology and structure. Studying these films and interfaces at high spatial resolution has previously been challenging given their soft nature and scale. Using electron transparent cross-sections prepared with a focussed ion beam (FIB), high resolution transmission electron microscopy (HRTEM) has been used to probe the local crystallography of three archetypical organic photovoltaic device structures grown on silicon and indium tin oxide (ITO). In HRTEM images lattice fringes of unprecedented clarity are observed, validating the optimised FIB method. HRTEM examination of device structure cross-sections on silicon reveals lattice fringes throughout pure films of CuPc and C60. The structure of the CuPc thin film can be correlated with bulk characterisation methods however, the observation of stacking faults demonstrates film non-uniformity. Lattice fringes in C60 films show an orientation preference with respect to the interface, which allows conclusions to be made about C60 when grown on molecular films. Mixed films show no lattice fringes. Structures grown on ITO are more complex than those on silicon, which is attributed the relatively rougher growth surface. Due to this rougher surface, the morphological changes occurring result in reduced crystallinity, a conclusion supported by bulk characterisation methods. The cross-sectional methodology has been extended to thicker films, revealing the presence of structural deviations that lie parallel to the surface. Scanning transmission electron microscopy, in combination with energy dispersive X-ray spectroscopy, high resolution quantitative compositional mapping reveals the morphology of the interface for the structures studied. This been correlated with the morphology of single CuPc film surfaces, with the conclusion that morphology of the CuPc surface remains unchanged after C60 film growth.

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No description available.

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No description available.