Metal clusters have been produced by condensation of metal atoms on or inside small argon clusters and by collision of supersonic atomic argon beams with atomic metal vapours. A key parameter in both processes is the metal atom particle density. For iron, metal particle densities above a thermal open crucible-type evaporator were determined using quartz-micro-balance mass flux measurements, revealing a point-source-like dependence on the distance from the crucible. For silver atoms the particle densities were also determined using scattering from small argon clusters. Formation and soft-deposition of iron nanoparticles was first attempted using a supersonic beam of argon atoms that was blown into a vapour of iron atoms. Transmission electron microscopy showed the presence of iron nanoparticles whose size depended on the deposition time, showing that aggregation takes place after deposition. The deposition rates were of the order of 0.01 nm/s. In the second part of the study argon clusters containing on average 21 atoms were directed through vapours of xenon or silver atoms. Time-of-flight mass spectrometry showed the presence of xenon and silver clusters when the xenon or silver particle densities were increased. The xenon clusters contained up to four atoms whereas silver would only formdimers. The mass spectra also showed argon atoms attached to the xenon clusters, but not to the silver dimers, which was attributed to the high temperature of the silver dimers.

Aerosols are an important factor of the Earth climatic system and they play a key role for air quality and public health. Observations of the Oxygen A-Band at 760 nm can provide information on the vertical distribution of aerosols from passive sensors, that can be of great interest for operational monitoring applications with high spatial coverage if the aerosol information is obtained with sufficient precision, accuracy and vertical resolution. To address this issue, retrieval simulations of the aerosol vertical profile retrieval from Oxygen A-Band observations by GOSAT, the upcoming OCO-2 and Sentinel 5-P mission and the proposed CarbonSat mission have been carried out. These simulations suggest that such observations will be useful in the measurement of uplifted aerosols such as volcanic plumes and forest fires. Retrievals from GOSAT were also undertaken that showed promising results in challenging conditions, warranting further study. The Fabry-Perot Etalon spectrometer provides a compact, robust and affordable alternative to grating or Fourier transform spectrometers. Such an instrument was designed and optimised for the measurement of aerosol in the Oxygen A-Band and its performance simulated in comparison to GOSAT, where it competed well despite its low cost. Initial calibrations of the instrument were undertaken and showed promising results in the instrument operation concept. Following on from this simulations were used to study the performance of groundbased observations showing that using and combining a range of viewing angles would contribute significantly to the vertical information content whereas polarisation proved not to be useful except possibly in extreme circumstances.

Atmospheric water vapour is an important (natural) greenhouse gas, infuencing both directly and indirectly the global radiative balance of the Earth as well as heat and moisture fluxes at the surface. Since water vapour concentrations may change as a result of surface warming and other environmental/meteorological factors, there is a need to understand the long-term behaviour. Changes are small, so it is critical to use high quality data with well-defined uncertainties and biases, particularly for climate research. Hyper-spectral infrared (IR) sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS) allow for higher vertical resolution profile measurements of water vapour to be obtained compared to their predecessors. First results of global comparisons of AIRS profiles show that for tropospheric layers between 925-374 hPa biases are within +-10% and a significant dry bias of 20% in regions of the upper troposphere, consistent with recent comparisons to reanalysis. A consistent approach to the retrieval of temperature and water vapour profiles from all hyper-spectral IR sounders is outlined and an initial set of retrievals from IASI at global climate sites is performed. Results from the University of Leicester Water Vapour Processor (UoL-WVP) show errors of ≈1 K and Atmospheric water vapour is an important (natural) greenhouse gas, infuencing both directly and indirectly the global radiative balance of the Earth as well as heat and moisture fluxes at the surface. Since water vapour concentrations may change as a result of surface warming and other environmental/meteorological factors, there is a need to understand the long-term behaviour. Changes are small, so it is critical to use high quality data with well-defined uncertainties and biases, particularly for climate research. Hyper-spectral infrared (IR) sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS) allow for higher vertical resolution profile measurements of water vapour to be obtained compared to their predecessors. First results of global comparisons of AIRS profiles show that for tropospheric layers between 925-374 hPa biases are within +-10% and a significant dry bias of 20% in regions of the upper troposphere, consistent with recent comparisons to reanalysis. A consistent approach to the retrieval of temperature and water vapour profiles from all hyper-spectral IR sounders is outlined and an initial set of retrievals from IASI at global climate sites is performed. Results from the University of Leicester Water Vapour Processor (UoL-WVP) show errors of ≈1 K and ≤20% within the troposphere for temperature and humidity respectfully. The significance of surface characterisation at a sub-pixel level is also demonstrated. Retrievals from IASI at selected climate sites for 2012 are inter-compared in a three-way analysis with high resolution radiosonde profiles and AIRS data. Results show that the mean standard deviation of observational error for IASI is 2.2% while AIRS is 3.6%. This thesis work represents a step forward in the use of AIRS and IASI data for climate research. However, proven long-term stability is needed for the water vapour data question to be answered. and humidity respectfully. The significance of surface characterisation at a sub-pixel level is also demonstrated. Retrievals from IASI at selected climate sites for 2012 are inter-compared in a three-way analysis with high resolution radiosonde profiles and AIRS data. Results show that the mean standard deviation of observational error for IASI is 2.2% while AIRS is 3.6%. This thesis work represents a step forward in the use of AIRS and IASI data for climate research. However, proven long-term stability is needed for the water vapour data question to be answered.

This thesis presents submillimetre (submm) observations using the James Clerk Maxwell Telescope (JCMT) Submillimetre Common-User Bolometer Array 2 (SCUBA-2) of dusty, luminous, high-redshift galaxies. Submm wavelengths are important because the coldest dust properties can be observed, which can help with the calculation of total infrared (IR) luminosities. Three samples of galaxies are investigated in Chapters 3, 4 and 6. The galaxies in Chapter 3 are selected using the Wide-Field Infrared Survey Explorer (WISE) with extremely red mid-IR colours. From previous studies these galaxies are a rare population of dusty, hot (60 - 120K), high-redshift 1 < z < 3, hyper-luminous galaxies and are known as hot dust-obscured galaxies (WISE-selected Hot DOGs). The galaxies in Chapter 4 are selected in a comparable method but are also radio-selected. These galaxies with radio emission are thought to have radio-jet dominated feedback. The galaxies from Chapter 3 and 4 are amongst the most luminous galaxies in the Universe and could be undergoing intense AGN-driven feedback. This feedback could be the result of major mergers between two gas-rich galaxies and are thought to be an important mechanism in galaxy evolution. Chapter 5 compares the two samples of galaxies in Chapters 3 and 4 and also their environments. The environments around high-redshift far-IR and mid-IR luminous galaxies appears to be above average. The overdense environments could yield evidence for the nature of their massive dark matter halos and highlight their bias as compared with the underlying dark matter distribution. The galaxies in Chapter 6 were selected in the millimetre (mm) wavelengths using Planck to have dusty spectral energy distributions (SEDs). Submm observations are used to determine if they are candidates for dusty, luminous, high-redshift galaxies and to obtain more accurate positions. Consequently this will help future searches of dusty, luminous, high-redshift galaxies using successive all-sky Planck data releases.

Studies of the rotation of disk galaxies have long been used to infer the presence and distribution of dark matter within them. Here I present a new Markov Chain Monte Carlo (MCMC) method to explore the extensive and complex parameter space created by the possible combinations of dark and luminous matter in these galaxies. I present exhaustive testing of this method to ensure it can retrieve dark matter halo parameters from artificial data, and apply it to real galaxies from The HI Nearby Galaxy Survey (THINGS) and other sources. The results of these studies can shed some light on how disk galaxies form and evolve. Chapters 1 and 2 provide background for the physics and statistical methods respectively. Chapter 3 shows the testing of the MCMC method on artificial data, and applies it to DDO 154 to find a more robust constraint on the inner log slope than previous methods. Chapter 4 applies this method to a broad range of galaxies taken from the THINGS survey, constrains their physical properties, and presents a simple model of feedback to compare with. Chapter 5 applies the method to M33, mapping a degeneracy between the log slope of the dark matter halo and the mass-to-light ratio, that excludes the combination of a cored halo and a light stellar disk. Chapter 6 extends the MCMC method to an earlier stage of analysis by marginalising over the parameter space of possible disk models for simulated galaxies. Chapter 7 presents conclusions and discusses future work that can lead on from this thesis.

This thesis work is concerned with the accretion processes and flow structures associated with stellar winds in binary systems. I study mass transfer via stellar wind capture in symbiotic recurrent nova RS Ophiuchi, using Smoothed Particle Hydrodynamics. I investigate the modes of mass transfer from the mass-losing star to the mass-accreting companion by implementing wind expansion based on the analytical Parker solution for isothermal winds. Mass capture fractions are calculated and found to be dependent on the velocity of the wind. The structure of the accretion discs formed is also investigated. The results show that all the accretion discs have radial extents larger than the predicted stability radius against thermal viscous instabilities. It is nevertheless found that the surface density profiles of the accretion discs are too low to trigger such disc outbursts. I also explore the effect of rotation on mass transfer and disc morphology. I also study the interaction between the transiting hot Jupiter WASP-12b and its host star, using ZEUS-2D and SPH-3D to simulate the planetary magnetosphere interactions with the stellar wind self-consistently. I attempt to model NUV absorption due to enhancements in density at the bow shock ahead of the planet. The numerical results show that the bow shock is always weak and broad due to the modest wind Mach number at the planetary distance. I compute theoretical UV light-curves from the hydrodynamic models and use a grid of stellar wind, planetary magnetic field strength and wind opacity parameters to show how the UV light-curves depend on different physical model parameters. The results show consistency with the existing UV data for WASP-12b. I also model two other transiting hot Jupiters and show that additional UV observations of more massive short-orbit hot Jupiters should distinguish clearly between different models for circumplanetary absorption.

The aim of this thesis was to further our understanding on the surface dynamics of silicon nanoparticles deposited on Highly Oriented Pyrolytic Graphite (HOPG) using non-contact Atomic Force Microscopy (NC-AFM) with the longer term aim of developing practical applications. Silicon nanoparticles in liquid were produced using sputtering gas aggregation by co-depositing with water in an ultrahigh vacuum (UHV) environment (von Haeften 2009). Water was sprayed into the system with custom designed apparatus onto a cold target cooled with liquid Nitrogen (LN2) to form an ice matrix. The melt from this ice matrix was then collected and diluted with isopropanol (IPA) and drop cast onto HOPG. Analysis using X-ray Photoelecron Spectroscopy (XPS) confirms the existence of silicon in liquid suspension, and that the silicon exists in high oxidization states. AFM investigations suggest the minimum size of these nanoparticles to be 0.8 nm; however it was seen that the size of the nanoparticles shifts depending on which layer on the HOPG substrate they have been deposited on. Formation of the nanoparticle film layers was also observed when changing the dilution of the nanoparticle solution using IPA. The growth mode of the nanoparticles was determined to be the Stransky- Krastanov mode. NC-AFM measurements related to the surface dynamics of the nanoparticles revealed that silicon nanoparticles on HOPG surfaces show rich surface dynamics. The diffusion coefficient of many active nanoparticles undergoing Brownian-type motion was calculated. Besides this, the change in shape and size of very active circular nanostructures on the HOPG surface are detected and tracked. Strong evidence were found to suggest that the dynamical changes are related to the effect(s) of the AFM tip, due to induced impulsion upon nanoparticles. Many other examples related to the tip impulsion effect upon nanoparticles are presented. Self-assembly mechanisms of nanoparticles are observed and exemplified. In addition, evidence for the stability of the nanoparticles – demonstrated by example – is presented.

Supermassive black holes (SMBHs) are believed to reside at the centres of most galaxies. Observations suggest that the host galaxies are strongly affected by feedback produced by accreting SMBHs. Feedback in the form of ultra-fast outflows (UFOs), which are expected to interact with the interstellar medium (ISM), have been used to explain scaling relations between SMBHs and their host galaxies. Such relations suggest that the feedback and ISM must couple very weakly, however, it is not clear how this is achieved. In this thesis I provide observational tests to constrain UFO shock physics. I show that if UFO shocks cool via inverse Compton (IC) scattering, they should be observable in X-rays, but are not actually seen. The likely explanation for this is that the outflow is in a two-temperature, non-radiative regime. This implies that AGN outflows do not loose their kinetic energy to radiation and that an alternative energy loss mechanism is needed to explain the weak coupling required. I use high-resolution simulations to investigate an UFO impacting upon a turbulent ISM. Complex processes occur in the turbulent medium, such as the detachment of mass and energy flows, which are missed in a homogeneous medium. While the shocked UFO can escape through low density regions, high density clumps are resistant to feedback and can continue to have negative radial velocities. Energy losses in the multiphase ISM may provide an alternative to the IC radiative loss mechanism. Given the importance placed upon simulations in aiding our understanding of AGN feedback, I present a resolution study using a commonly employed sub-grid feedback prescription. I find that changes in resolution impact upon feedback efficiency, although not necessarily in a systematic way. I therefore suggest caution when analysing simulation results in order to ensure that numerical artefacts are not interpreted as physical phenomena.

This thesis discusses the modelling and development of the Cherenkov detectors fielded at the National Ignition (NIF) and Omega facilities to measure observables important for improving understanding of inertial confinement fusion (ICF). It begins with an overview of ICF together with an introduction to the relevant laser facilities, theory and detectors. The Geometry and Tracking Version 4 (GEANT4), Monte Carlo Neutron Program (MCNP) and ACCEPT Monte Carlo codes were benchmarked and then validated experimentally at the high-intensity source facility using two Cherenkov detectors. GEANT4 was subsequently used for calculations of temporal response and light production from the Cherenkov detectors; thus allowing GRH's +-50 ps uncertainty to be achieved and improved measurements of the DT γ/n strength (4+-2 +-10-5) and DT γ spectral shape to be made. Building on this, the novel Prompt Areal Density Diagnostic (PADD1) was also designed to enable measurements of remaining shell at peak fusion reactivity. Limitations of the existing Cherenkov detectors are then introduced, specifically the photomultiplier tube (PMT) which limits bandwidth to 88 ps. Following an investigation into alternative technologies, Chemical Vapour Deposition (CVD) diamond emerged as a possible dynode candidate due to high secondary electron emission ( > 20), significantly better than lead glass (1-3) used in micro-channel plate (MCP) PMTs. A CVD diamond transmission dynode < 100 nm thick could be incorporated into a PMT analogous to an MCP. Despite diamond's potential there are parameters, such as boron doping, surface termination and crystallinity which impact yield and require optimisation through experiment and simulation. A study of secondary electron modelling theory and limitations was thus performed, and an approach utilising an experimentally-derived dielectric function incorporated into the GEANT4 toolkit. This low-energy extension combined with measurements of diamond's emission characteristics will be used in the future to facilitate diamond's integration into a PMT.

The influence of topography on crystal nucleation is investigated, mostly with regards to nucleation from vapour but also regarding nucleation from the melt and from solution. Two mechanisms are discussed for acute features to promote nucleation: a thermodynamic reduction in the free energy barrier provided by a favourable geometry, and the formation of a confined condensate of a metastable phase which then transitions to the crystalline phase. Organic compounds nucleating from vapour are used to demonstrate the efficacy of scratches and mineral steps as preferable nucleation sites. A study of various compounds on mica demonstrates that highly acute features provide the most favourable nucleation sites. High-magnification study of the growth of crystals from such features reveals the presence of small condensates prior to the appearance of bulk crystals, and the growth of these is studied quantitatively. Ice is shown to have a similar nucleation site preference to the organic compounds, although no condensate was seen prior to bulk nucleation. Well-defined 100 nm-wide trenches were milled into silicon substrates and shown to have a great ability to direct ice nucleation. The freezing of picolitre droplets of water was studied on smooth and roughened silicon, glass and mica substrates, and the roughening was shown to have little to no effect. Calcium carbonate growth and its dependence on topography was investigated, and found to be broadly anomalous and greatly dependent on surface chemistry.