The hydrated electron attracts attention since its discovery over fifty years ago. Being one of the products of the ionization of water, hydrated electrons, which are free electrons in water, play significant roles in biological damage, atmospheric chemistry, nuclear chemistry, etc. However, despite its importance and the large number of studies on the hydrated electron many aspects of it are still not resolved. One of these concern its existence and behaviour at the water surface, which is of great interest since many of the processes it is involved in take place at interfaces. In this work, a technique is developed, that is based on the second harmonic generation (SHG) and enables the study dynamics of the hydrated electron at the water/air interface. By introducing a local oscillator, which interferes with obtained SHG from the water surface, a signal directly proportional to the sample concentration is obtained, in contrast to the quadratic dependence from conventional SHG. Moreover, the technique allows phase information to be obtained, which enables the determination of the real and imaginary parts of the 2nd order non-linear susceptibility. In addition to this, the technique uses a lock-in measurement, removing large constant offset from the interference. The technique yields high quality data on adsorbates with low surface concentration and has been extended to the time domain which provides insight into the dynamics of hydrated electrons at the water/air interface. In this experiment, the electron was generated using the charge-transfer-to-solvent transition of iodide and probed primarily over the first few picoseconds. This probes the initial solvation of the electron at the interface. Our results suggest that the dynamics are similar to the dynamics observed in the bulk, although the added phase-sensitivity provides new information about early solvation dynamics.

This thesis presents theoretical models and results of numerical simulations describing the propagation of optical pulses through dense, thermal atomic vapours. In particular we investigate the nonlinear effects of optical solitons due to self-induced transparency (SIT) in two-level systems, optical simultons in V-type three-level systems and electromagnetically induced transparency (EIT) in Λ-type systems, including the storage and retrieval of dark-state polaritons. An investigation is made into two-photon excitation of the 5D states of rubidium in a high-intensity beam including the hyperfine structure of the relevant atomic levels. Decay from these states to the 6P manifolds is ruled out as a cause of experimentally observed fluorescence due to the amount of power broadening associated with intensities necessary to provide any significant level of population in these highly excited states. We combine the nonlinear effects of optical solitons and EIT to explain experimentally observed steepened pulses in a V-type system in a micron-length cell. We explain the behaviour as the early formation of a simulton pulse drawn from a CW probe field by a strong coupling pulse, due to coherent population trapping. We predict that in a longer cell it may be possible to facilitate propagation of matched pulses, even when the transitions in the system have different propagation coefficients, as long as decoherence from collision broadening can be controlled. The fact that weak pulses can propagate with this scheme suggests an approach to achieving transparent propagation of single or few photon pulses distinct from, but related to, both SIT and EIT.

All optical fields are inherently of statistical nature undergoing random fluctuations. The underlying theory of fluctuating optical fields is known as coherence theory and partial polarization. This thesis describes the experimental study on the coherence and polarization measurements for statistical optical fields. Particular emphasis is placed on the full field visualization for coherence function and coherence matrix, and its application to the study of changes in random optical fields on propagation. The thesis consists of 9 chapters including Chapter 1 devoted to introduction. Chapter 2 proposes a novel optical geometry for the full-field coherence visualization to study the coherence diffraction. The non-diffracting solutions for the coherence function and the coherence interference phenomena have been presented in Chapter 3 and Chapter 4, respectively. As the application, Chapter 5 presents the experimental demonstration of the coherence holography to synthesize the arbitrary spatial coherence function. To take the vector nature, Chapter 6 and Chapter 7 develop our optical geometry for the full-field visualization of coherence polarization matrix to study of the stochastic electromagnetic fields on propagation. The principle of coherence tensor holography is proposed in Chapter 8 and experimentally demonstrated for the first time. At last, conclusions and future works have been given.

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Forster Resonance Energy Transfer (FRET) is the non-radiative transfer of energy from an initially excited donor to an acceptor via a dipole-dipole interaction: FRET ~ modified donor fluorescence decays are dependent on the donor .:.. acceptor distance distribution function p(r) . This function contains valuable structural information regarding the slirroundings of the probe molecules. Currently the form of this function is assumed and then the calculated function is fitted to the measured decay via the Least Squares Method to determine the best fit parameters. Fluorescence Nanotomography (FN) is an ambitious technique developed within the Photophysics group that attempts ·to recover p(r) from FRET - modified fluorescence decays without making a speCific assumption regarding its form [1]. Instead p (r) is represented in tenns of a series of Laguerre polynomials. The ability to directly recover p (r) would make FN a po~erful structural sensing tool. However this· is a non - trivial technique requiring the solution of two inv'erse problems. 'The first is to. recover the pure' fluorescence response. ~ (1) from the measured fluorescence decay F (1). This problem was solved using the Maximum Entropy Method (MEM) which reconstructs the most probable lifetime distribution consistent with the measured decay. FN was then used to recover the form of p(r) from the MEM lifetime 'distribution. This thesis characterises' FN by applying it to calculated functions, synthetic decays and measured decays of Perylene and C02+ in glycerol and incorporated into silica gels, controlled Pore Glasses and in lipid bilayers. It was found that the physical information contained within the lifetime distributions recovered from the FRET modified decays using 'MEM is not adequate to enable the recovery of an absolute arb~trary donor - acceptor distance distribution. Therefore more specific prior information regarding the form of p(r) is required. .A more detailed study of the FRET kinetics ofPerylene and Co2 + encapsulated in a Tetramethyloxosilane (TMOS) gel is also presented here. This is analysed using the least squares method and illustrates the variety of factors affecting the FRET kinetics in a complex environment.

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