The object of this research was the construction of a microwave spectroscope at 1.25 cm. wavelength. The double modulation method, which was used here, is discussed. The system was tested with ammonia, and the inversion spectrum identified. The effect of using various harmonies of detection is shown. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This research work focused on studying the emission spectroscopy produced from the high energy ion-molecule collision processes in mass spectrometry. The collision experiments are described and divided into 4 chapters (Chapter 3, 4, 5, 6).N2O+● is an ion of atmospheric importance. In chapter 3 the investigation of the collision between high translational energy (4-8 keV range) N2O+● ions and Helium target gas in mass spectrometry using collision induced emission (CIE) spectroscopy is described.In chapter 4, the collision-induced emission (CIE) spectra from 4-8 keV collisions between projectile He+● ions and CO2 target gas (He+●/CO2) were obtained. In Chapter 5, to probe the validity of this hypothesis, CIE experiments were carried out to observe the photon emissions from keV collisions of a selection of projectile ions with O2 target gas. By studying the resulting CIE spectra, a second potential mechanism came to light, one that involves the nearly isoenergetic O2+. A → X state transition. In chapter 6, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as recovery signals in neutralization-reionization mass spectrometry in the modified VG-ZAB mass spectrometer.

Gelsolin was labelled with the sulphydryl-specific fluorescent reagent 6-acryloyl-2-dimethylaminonaphthalene (acrylodan). The degree of labelling using non-denaturing conditions was 1.9 ± 0.5 acrylodans per gelsolin molecule. Circular dichroism and viscosity studies showed no significant effect on gelsolin structure and function on incorporation of the label. Circular dichroism studies did not detect Ca²⁺ effects on aerylodan-labelled gelsolin, but fluorescence studies detected subtle changes in the protein. The presence of Ca²⁺ causes a decrease and red-shift in fluorescence emission, an increase in sensitivity to quenching by I⁻ and a decrease in fluorescence polarisation of the acrylodan-labelled gelsolin. These indicate an increased degree of exposure of the fluorescent label to the solvent environment on interaction of gelsolin with Ca²⁺. Actin binding to gelsolin was evident from a decrease in fluorescence intensity, an increase in sensitivity to quenching and an increase in fluorescence polarisation. Actin binding increases the exposure of the acrylodan label to solvent, as does Ca²⁺ binding. / Science, Faculty of / Chemistry, Department of / Graduate

Fluorescence spectroscopy can be used to probe protein conformation and is recognized as a technique that provides very specific information. It has been applied/ in recent years/ to the study of tropomyosin (TM) and its role in regulation of contractile processes. In this thesis, two different approaches were used to further the understanding of the structure/function relationship in the two chain coiled coil of tropomyosin. The first involves a comparative study on TM and non-polymerizable TM (NPTM) (Mak, A.S., and Smillie, L.B. (1981) Biochim. Biophys. Res. Commun., 101, 208-214). Fluorescence involving pyrene (Py) and acrylodan (AD) bound at the only cysteine residue in the molecule (Cys-190), and circular dichroism (CD) studies led to the main conclusion that, while the two species, are very similar in stability, the COOH-terminus is required to hold the Cys-190 region in a specific conformation. This long-range structural effect may play a role in regulation of contraction. A species having one intact COOH-terminus, made by hybridizing TM and NPTM, was found to be non-polymerizable suggesting that one intact COOH-terminus is insufficient to permit overlap with the NH₂-terminus of a neighbouring TM under polymerizing conditions. Unlike the TM/NPTM hybrid, the hybrid of TM and platelet TM (P-TM) was difficult to make due to the sequence mismatches in the terminal regions, but small quantities could be detected by loss of excimer fluorescence from Py-P-TM on rapid cooling of a heated mixture of Py-P-TM and cardiac TM (C-TM). The second approach was to investigate the effect of actin-binding proteins on the structure and function of tropomyosin. DNase I depolymerizes F-actin and is known to interfere with the end-to-end polymerizability of tropomyosin (Payne, M.R., Baydoyannis, H., and Rudnick, S.E. (1986) Biochim. Biophys. Acta 883, 454-459). Results presented here from fluorescence studies suggest that this effect is caused by a localized loss of structure in the tropomyosin at the sites of labelling upon binding of DNase I. This result is supported by CD studies on labelled and unlabelled tropomyosins. Gelsolin is another actin-binding protein found in many cell types and in extracellular fluids. It is shown here to be able to depolymerize tropomyosin, but its mechanism of action is not the same as that of DNase I. The effect of interaction of gelsolin on the structure of tropomyosin, as determined from fluorescence studies, is negligible. / Science, Faculty of / Chemistry, Department of / Graduate

The binding energies and momentum distributions of all of the valence orbitals of (CH₃)₂O, PH₃, CH₄ and SiH₄ have been measured by high momentum resolution electron momentum spectroscopy. The binding energy spectra have been compared to Green's function and configuration interaction calculations from the literature and with new calculations performed in collaboration with co-workers at Indiana University and Universitat Braunschweig. For PH₃, CH₄ and SiH₄, near Hartree-Fock limit calculations of the momentum distributions and very accurate calculations of the ion-neutral overlap using MRSD-CI wavefunctions to describe the ion and target have been performed in collaboration with co-workers at Indiana University. Good agreement is obtained between the (CH₃)₂O measurements and the momentum distributions calculated from relatively simple wavefunctions, except in the case of the outermost orbital. The effects of diffuse and polarization functions in the basis sets, and also the influence of molecular geometry, have been investigated. Comparison of the momentum distributions of the outermost orbitals of H₂O, CH₃OH and (CH₃)₂O demonstrates a delocalization of charge density with methyl substitution. The measured momentum distributions of PH₃, CH₄ and SiH₄ are compared with near Hartree-Fock limit calculations as well as ion-neutral overlap calculations in which the ion and neutral wavefunctions are described by multireference, singly and doubly excited, configuration interaction calculations. In each case, the experimental results are well modelled by the near Hartree-Fock limit calculations, and there is little difference between the Hartree-Fock limit and ion-neutral overlap calculations. A significant splitting of the 4a₁ (inner valence) pole strength is observed for PH₃, but the inner valence strength is largely contained in the main peak for both CH₄ and SiH₄. Green's function calculations quantitatively reproduce these results. Ion-neutral overlap calculations using MRSD-CI wavefunctions to describe the ion and target have been performed for HF, HCl, Ne and Ar. These are compared with previously published EMS measurements of the momentum distributions. Very poor agreement between theory and experiment is obtained for HF and HCl. The theoretical and experimental results for all of the hydrides CH₄-HF and SiH₄-HCl as well as Ne and Ar are reviewed. / Science, Faculty of / Chemistry, Department of / Graduate

The optical properties of the 10.4 K organic superconductor, κ-{BEDT—TTF)₂[CU-(NCS)₂], are the subject of this thesis. This organic superconductor is a crystalline solid consisting of planes of BEDT-TTF molecules separated by planes of Cu{NCS)₂ anions. The arrangement of molecules results in electrical two-dimensionality, with high conductivity within the planes of BEDT-TTF molecules and poor conductivity in the perpendicular direction. Until the recent discovery of an organic superconductor with TC = 11.5 K, the 10.4 K transition of (BEDT-TTF)₂[Cu(NCS)₂] was the highest in the class of organic metals. Optical properties of superconductors have played an important role in analysis of their unusual properties. Using single crystals of (BEDT—TTF)₂[Cu(NCS)₂] and light polarized within the highly conducting plane, I have measured both specular reflectivity and bolometric absorption over a wide region of the infrared spectrum. The reflectivity measurements cover most of the far and mid-infrared for both protonated and deuter-ated compounds, with sample temperatures between 300 K and 6.5 K. The resulting spectra show contributions from electronic interband transitions, intraband transitions, and molecular phonon vibrations. A search for the superconducting energy gap was undertaken using the bolometric technique to measure the sample absorption at far-infrared energies. These measurements were performed at temperatures below Tc and cover the part of the spectrum where condensation of electrons into superconducting Cooper pairs should be directly observable optically. On other materials, measurements in this part of the spectrum have directly revealed the binding energy for the superconducting electron pairs, and have been instrumental in showing that details of the electron-phonon interactions are very important in superconducting systems. In the spectra which we have measured, any effect of the superconducting transition is overwhelmed by other contributions to the absorption in the far-infrared energy region. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The suitability of using a Nal crystal as a fast coincidence gamma ray detector was investigated using the multichannel "fast-slow" delayed coincidence method to obtain prompt time resolution curves with a Na²² gamma ray source at Nal temperatures of 170, 185, 200°K. A comparison of the time resolution curve obtained using two NE 102 plastic scintillators (FWHM: 640 psec) with that using a cooled Nal scintillator and a NE 102 scintillator (FWHM: 680-psee) showed that Nal is a satisfactory fast coincidence gamma ray detector at 185°K. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new technique has been devised to obtain time-resolved measurements of small spectral line shifts. Two linear neutral density wedges with opposite transmission gradients were placed over the top and bottom of a monochromator exit slit in such a way that a wavelength shift of a spectral line resulted in a change in light intensity transmitted through the wedges, which was monitored by two photomultipliers. To test this technique, an N II line, for which Griem has calculated the Stark shift as a function of electron density, was observed in the emission spectrum of a small theta-pinch using a monochromator of 10 Å/mm inverse dispersion. Space and time resolved line shift measurements were made and were associated with the axial velocity and the electron density fluctuations of the plasma. An uncertainty of 0.015 Å was estimated, which, for the 1.5 Å line used, corresponds to a shift to width ratio of 10⁻², believed to be lower than any previous shift measuring technique. Time of flight velocity measurements and conservation of mass considerations have confirmed the results as both reasonable and self-consistent. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An investigation into the potential of time-wavelength resolved luminescence spectroscopy for the analysis of inorganic powders was performed. A time-wavelength resolved luminescence spectrometer consisting of an excimer laser, scanning monochromator, and gated integrator was constructed. The spectrometer had wavelength coverage from 265 nm to 800 nm, it was capable of measuring lifetimes between 100 ns and 500 ms. Sample excitation was done at 193 nm and 248 nm. A luminescence system model of first order decay in the time domain and a Gaussian function for the emission band was assumed. The time-wavelength resolved luminescence spectrum was described by the parameters: lifetime, peak maxima, peak halfwidth, and intensity factor. Parameter estimation was done with an algorithm employing a linear algebra construct and simplex optimization. The algorithm's performance on highly overlapped spectra was evaluated. For two component mixtures having a 1 % RSD noise level, overlaps greater than 0.3 halfwidths in the spectral domain and lifetime ratios greater than 1:1.3 were resolved with all parameter estimates having an error of less than ±2%. The luminescence spectra of CaMo0₄, SrMo0₄, BaMo0₄, ZnMoO₄, CdMo0₄, PbMoO₄, CaWO₄, SrW0₄, BaWO₄, ZnWO₄, CdW0₄ and PbWO₄ consisted of broad featureless bands showing simple exponential decay. Mixed crystals of Ca(MOxW₁-x)O₄ and Sr(MOxW₁-x)0₄ were examined. Tungstate emission was quenched by molybdate, the molybdate emission dominated when x was greater than 0.15. The tungstate lifetime was found to be proportional to molybdate concentration. The luminescence spectra of CaZrO₃, SrZr O₃, BaZr O₃ CaHfO₃ SrHfO₃, BaHfO₃, CaO, SrO, and BaO as pure compounds and doped with T1, Pb, Sb, and Bi were studied. The pure zirconates and hafnates showed short lived (<100 ns) luminescence with 248 not excitation; no readily discernible luminescence was observed with 193 nm excitation. Doped compounds tended to show luminescence characteristic of the dopant ion. / Science, Faculty of / Chemistry, Department of / Graduate

The application of Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) to the determination of total oxygen, nitrogen and sulphur in organic solution has been studied. Near-infrared emission lines of the three nonmetals have been used and detection limits in xylene have been established. Oxygen was determined for the first time by ICP-OES in a nongaseous sample. The characteristics of the inductively coupled plasma when used with an organic aerosol have been studied with respect to the completeness of atomization and potential interference from the complex excitation environment. Spatially resolved atomic and molecular emission profiles have been collected as part of these investigations. The nonmetal emission intensities were found to depend on the boiling point of the compounds containing the nonmetal because a redistribution effect in the nebulizer chamber was leading to an enrichment of volatile solutes in the aerosol stream to the plasma. Response factors for a series of compounds have been determined. The utility of the method was shown by establishing working curves and by testing certified standards for sulphur. / Science, Faculty of / Chemistry, Department of / Graduate