An accurate and quantitative description of the amorphous phase is necessary to understand a correlation of structure with properties for polymeric materials, especially as these evolve with time. Due to the lack of long-range order, the analysis of the amorphous phase in polymers has been difficult and has yielded only limited information. Flory's rotational isomeric states (RIS) model provides a useful characterization of the short-range order for chains in the amorphous phase, and provides semi-quantitative information for an entire amorphous chain. In this research, experimental spectroscopic methods are combined with simulation of spectra based on superposition of normal coordinate analysis of RIS generated chains as applied to Poly(lactic acid) (PLA) and Poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)]. Due to the unusually high strain-induced crystallization in PLA, it is of great importance to understand the structural changes that accompany deformation. The change in conformational distribution induced by deformation of PLA is estimated based on comparison of changes in the observed Raman spectra with those in the calculated. Analysis of the amorphous phase of PVDF homopolymer and P(VDF-HFP) copolymer is motivated by the increasing use of these polymers in biomedical devices. Spectroscopic features that characterize the conformational structure were established by comparing experimental and simulated Raman spectra of these materials. Different RIS models were investigated and compared with the experimental spectra, leading to an assessment of the distribution of conformation in the amorphous phase. The dynamic behavior of the amorphous phase under external excitation is also of great interest, as this behavior is closely related to the physical properties of the polymer. In this research, the dynamics of amorphous chains were investigated through the response to microwave frequency excitation. Eleven different polymeric systems were studied as a function of temperature by microwave frequency dielectric spectroscopy. Relaxation processes were observed in polymer with low glass transition temperatures (Tg) and characterized on the basis of the temperature dependence of the relaxation. These relaxation processes all followed an Arrhenius temperature dependence. The activation energy was determined and compared to Tg, which strongly suggested that relaxation was by the Johari-Goldstein β process.

Previous methods of determining the complex permittivity, e* = e' - je", at millimetre wavelengths are reviewed, and at a wavelength of 0.848cms six different ways of determining this quantity from the experimental observations are compared. It is found that the method first described by Fatuzzo and Mason is the most suitable for determining the temperature variation of the complex permittivity at wavelengths of and 0.435cms, and the three sets of apparatus are adapted to cut down experimental errors to a minimum. The complex permittivity, for several simple liquids, is determined at each of the three wavelengths over a temperature range from 50aC down to the freezing point of the liquid The static permittivity Es and the refractive index at the Sodium-D line nD are also measured over this same temperature range. Assuming that the dispersion of E* is given by Debye's equations, then, knowing the static permittivity and the experimental value of E* at one other wavelength, the permittivity at the high frequency end of the dispersion curve E-infinity and the critical wavelength lambdac can "be calculated. Using the value of E* at each of the three experimental wavelengths in turn, three different values for E-infinity and lambdac at each temperature are calculated. The value of E-infinity and lambdac at 3.332cms are taken as the correct values, and the deviation of the values at the other two wavelengths from this value noted. This deviation is to smaller values of E-infinity and lambdac as the wavelength shortens and the deviation increases with decreasing 'temperature. This type of deviation is explained by the presence of a second absorption band centered at sub-millimetre wavelengths. By considering the amount of the deviation and the difference E-infinity - N&phis;2 as compared with ES - N&phis;2 it is concluded that; the second absorption band is due to a resonance absorption, rather than a Debye type absorption, and having a resonant frequency which decreases slightly with increasing temperature.

The excitation of liquids to produce optical amplification depends on a number of factors associated with the molecular properties and the intra molecular structure of liquids. The most important factors determining the efficiency of the activation process are the lifetimes of the states which decay to produce laser transitions and the various mechanisms by which the excitation may be by-passed, for example, by the excitation of triplet states of dyes. In a given column of excited liquid, the optical gain of the column will depend on the population inversion, the column length and the reflectivities of the mirrors defining the optical cavity. The latter mirror reflectivity may be enhanced by non linear optical processes in the liquid in the course of which hypersonic waves may be stimulated, or a stationary wave of thermal origin may be brought into existance which could introduce a periodicity of refractive index into the column. The purpose of this investigation is to design and develop a very fast flashlamp pumped dye laser system which will have an active lasing time period > 100 ns so that triplet state population and any major thermal effects become less important. The design parameters for ultrafast ultra violet lights sources are also investigated. The first part of the thesis considers the criteria required for the efficient optical excitation of a liquid and describes the design and construction of fast light sources. The properties of strip line pulsers are considered in detail, and the results from a series of prototype devices are evaluated. These include specially designed coaxial flash lamps as well as the usual linear type. Preliminary experiments and problems associated with achieving lasing output from rhodamine 6G are discussed.

An isoperibol solution reaction calorimeter has been constructed. The precision and accuracy of the calorimeter were checked by measuring the enthalpy of reaction of tris(hydroxymethyl)aminomethane, THAM, in:(a) excess 0.1 mol dm - aqueous hydrochloric acid(b) excess 0.05 mol dm -3 aqueous sodium hydroxide. The mean of 8 runs were: (a) DeltaH298 (1296 <n< 1780) = -29.87 0.05 kj mol-1. Literature: DeltaH298 = -29.790 + 0.031 kj mol-1, n=1345. (b) DeltaH298 (1241 <n< 1550) = +17.18 +/- 0.05 kJ mol-1. Literature: DeltaH298 = +17.177 - 0 . 0 2 3 kj mol-1.(n is the mole ratio of water to THAM.) From measurement of the enthalpy of hydrolysis the standard enthalpy of formation of rubidium tetrafluoroiodate has been derived: DeltaH0F(RbIF4, c)298= -1121.51 + 6.33 kj mol -1. Heat capacity measurements for RblF4 over the range 273-303 K are also reported. The standard enthalpies of formation of some alkali metal polyhalides have been derived from calorimetric measurements, in the isoperibol mode, of the enthalpy of reaction of the crystalline polyhalides with: excess aqueous silver nitrate (ii) excess aqueous sulphur dioxide. The following standard enthalpies of formation at 298.15 K are reported: DeltaH&deg;f (CsICl2,c) = -512.01 + 4.14 kJ mol-1; DeltaH&deg;f (RbICl2,c) = -492.31 + 4.12 kJ mol-1; DeltaH&deg;f (CsIBr2,c) = -446.32 + 4.08 kJ mol-1; DeltaH&deg;f (RbIBr2,c) = -429.11 + 4.22 kJ mol-1; DeltaH&deg;f (Csl3,c) = -359.79 - 5 .77 kJ mol-1; DeltaH&deg;f (CsICl4,c) = -571.91 + 6.90 kJ mol-1 and DeltaH&deg;f (RbICl4,c) =-554.36 i 6.99 kJ mol-1. (ii) DeltaH&deg;f (CsICl2,c) = -530.35 + 0.67 kJ mol-1; DeltaH&deg;f (RbICl2,c) = -461.36 + 1.40 kJ mol-1 and DeltaH&deg;f (Csl3,c) = -381.96 +/- 1 .05 kJ mol-1. The standard enthalpy of formation in (i) for Csl3 is in good agreement with literature values derived from e.m.f. studies and from dissociation pressure measurements. The standard enthalpy of formation of AglO3(c) and the enthalpy change for the process [formula] were also derived from calorimetric measurements to supplement the ancillary data required to calculate the standard enthalpies of formation listed above. 'Thermochemical radii' of the ions IC12, IBr2-,IC14- and I3- have been calculated by the Kapustinskii-Yatsimirskii procedure in order to estimate lattice energies of the salts listed in (i) and DeltaH&deg;f (lXn-,g) (where Xn = Cl2,Br2,Cl4 and I2). Additional lattice energies, standard enthalpies of formation and enthalpies of decomposition of other alkali-metal and alkaline-earth salts containing these ions are reported. 'Thermo chemical radii' of the ions Cl-,Br-,-~, N03-,S0₄2-,C103-,Br03- and I0 3 have been calculated to investigate the relationshipbetween the 'thermochemical radius' and the geometric size of an ion of given symmetry. Lattice energies of alkali-metal and alkaline-earth salts containing these ions have been estimated and compared with literature values.

The first chapter, of this thesis is devoted to the development of the theory for the ionization of an atom or ion by electron impact. We have pursued the particular approach adopted by Schiff and derived an expression for the triple differential cross section corresponding to the ionization process. Chapter 2 described alternative treatments of the problem and the various approximate models that have been used for calculations. Included amongst these approximate models is the first Born approximation and it is upon this that the calculations of chapters 3 and 4 are based. These calculations of the triple differential cross section for the ionization of helium by electron impact are restricted to impact energies below 260eV to enable a comparison with the experimental measurements of Ehrhardt et al. The calculations of Chapter 3 use a simple uncorrelated function to describe the target ground state and constitute a preliminary investigation of the TDC with particular regard to the relative importance of the direct, exchange and capture contributions. The results of these calculations indicate that the capture process makes negligible contribution to the TDC in the energy region considered and it is consequently ignored in the later calculations. In Chapter 4 the calculations of Chapter 3 are repeated using an accurate 6 configuration C. I. target wave function. The results obtained are compared both with experiment and results of calculations based on other approximate models. Finally in Chapter 5 we examine a number of points arising from the preceding chapters.

Studies of the kinetics of ion-molecule reactions associated with isobutane chemical-ionization mass spectrometry have shown that many of these reactions proceed via the formation of a collision complex which undergoes either unimolecular decomposition to reactants, or collision-induced decomposition to products. Rate constants for the formation of collision complexes between isobutane reactant ions and various ketones, nitriles, alcohols, and anisoles were obtained. Comparisons between these rate constants and collision frequencies calculated from the Average-Dipole-Orientation theory showed that, in general, the reactions proceeded with efficiencies less than unity. The lifetimes of most of the collision complexes were found to lie in the range 1-10 Psec. The relative efficiencies with which several compounds effected the collision-induced decomposition of the complex suggested that the third-body efficiencies were determined by the collision duration. Charge - transfer reactions between the isobutane reactant ions and anisoles occur by a direct mechanism. The magnitude of the rate constants for the formation of collision complexes were related to the structures of the compounds under study. For the reactions of certain reactant ions with the anisoles and halohydrins the rate constants were correlated with the appropriate substituent constants. It was suggested that differences between the mechanism proposed herein and that proposed by Field for the reaction between C4Hg+ and benzyl acetate were due to differences in sample-pressure ranges. Kinetic studies of the ion-molecule reactions consequent upon electron-impact ionization of methane and of isobutane, have suggested a novel method of estimation of reagent-gas pressures.

<p>Dissociative recombination is the process in which a molecular ion recombines with an electron and then fragments into neutral products. This process has been studied in many experiments over the years at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. In this thesis the experimental methods and data analysis procedures used to investigate dissociative recombination are presented together with the results for several diatomic and triatomic ions. Cross sections and branching fractions of the different breakup channels have been determined. An imaging system was introduced to study the fragmentation channels in detail. The main focus is on the dynamics of the three-body breakup of triatomic dihydride ions. This work includes the results from the dissociative recombination of NO⁺, SH₂⁺, SD₂⁺, PD₂⁺, NH₂⁺, CH₂⁺, H₂O⁺ and H₃⁺.</p>

Dissociative recombination is the process in which a molecular ion recombines with an electron and then fragments into neutral products. This process has been studied in many experiments over the years at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. In this thesis the experimental methods and data analysis procedures used to investigate dissociative recombination are presented together with the results for several diatomic and triatomic ions. Cross sections and branching fractions of the different breakup channels have been determined. An imaging system was introduced to study the fragmentation channels in detail. The main focus is on the dynamics of the three-body breakup of triatomic dihydride ions. This work includes the results from the dissociative recombination of NO+, SH2+, SD2+, PD2+, NH2+, CH2+, H2O+ and H3+.

This thesis presents experimental results on molecular spectroscopy of gas phase molecules using synchrotron radiation. It deals mainly with dynamical processes following resonant excitation of electrons from core and inner-valence shells of the following systems H2O, H2, SF6 and CD4. In order to reach these deep electrons and excite them photons in the energy range from 25 to 550 eV were used, depending on the particular system. Two experimental techniques are used. Photon induced fluorescence spectroscopy is used to study the fluorescence emission of fragments after the decay of resonant coreexcited states for the water molecule, and after doubly excited states and resonant excitations of inner-shell electrons for H2 and SF6 respectively. Only the emission in the visible and near infrared range (300-900nm) and the Lyman-α transitions are measured. Energy resolved electron-ion coincidence is used for the study of the fragmentation of CD4 and SF6 after selective ionisation of one of the outer-valence orbitals. In the case of CD4 the fragmentation is compared for the cases in which the ionisation is done directly, or through participator Auger decay of different resonantly core-excited states. / QC 20100910

<p>To further the understanding and knowledge about fusion plasmas and their behaviour during different conditions, it is important to be able to collect information about the plasma and the processes occurring within it. Visible spectroscopy, or the study of the visible wavelength light emitted by the plasma, is a useful tool in this search for knowledge.</p><p>This thesis is based on experiments where visible wavelength light has been measured and analysed in order to determine quantities about the emitting source. Doppler shift measurements of spectral lines have been utilised to determine the toroidal rotation velocities of plasma impurity ions and to study the correlation with mode rotation and the effect of active feedback control of the resistive wall modes. Information on the impurities present in the plasma has been determined and the calibrated intensities of spectral lines has yielded impurity concentrations, particle fluxes and electron temperature and densities. Ion temperatures have been determined from Doppler broadening measurements.</p><p>The measured vibrational and rotational band structure of deuterium molecular spectra has been analysed in order to calculate rotational and vibrational temperatures, relative populations and molecular particle fluxes. The effect of the molecular flux on simple calculations of atomic flux has also been studied. Specific molecular states and transitions of deuterium have also been probed with synchrotron radiation to study the level and transition energies.</p><p>The measurement and analysis of visible wavelength light has been demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and molecular structure.</p>