High resolution photoelectron spectra of a number of polyatomic molecules have been obtained using Zero-Kinetic-Energy Pulsed-Field-Ionisation (ZEKE-PFI) spectroscopy. The molecules studied were trifluoromethyl iodide (CF₃I), all three geometric isomers of the aminobenzotrifluorides (CF₃C₆H₄NH₂) and 4-fluorobiphenyl (C₆H₅V₆H₄F). The ground ionic state (²E_3/2) of CF₃I has been studied by two separate excitation schemes. The first involved a direct two-photon (one-colour) process from the neutral ground state. The spectrum observed was found to be very similar to that of the conventional photoelectron spectrum with progressions being observed in all three totally symmetric normal modes reflecting the direct Franck-Condon overlap between the two states. The spectrum is very different to that seen for CH₃I where long vibrational progressions were observed due to intermediate bond stretching. The lack of such effects in CF₃I is ascribed to the weakness of the one-photon absorption at the wavelength required for two-photon ionisation. A second excitation scheme involved a two colour (2 + 1') process via the [²E_3/2]6p Rydberg states. The ZEKE-PFI spectra obtained allowed the assignment of the majority of the vibrational structure of the intermediate. This structure, assigned to normal mode v₃ (the C-I stretch), has a vibrational frequency far lower (144 cm^-1) than either the neutral (286 cm^-1) or ionic (205 cm^-1) ground states. This is ascribed to interactions between the 6p Rydberg states and an ion-pair state. The aminobenzotrifluorides have been studied in a two-colour (1 + 1') scheme via the S₁ valence state. The high resolution of ZEKE-PFI spectroscopy allows the torsional structure of the ion to be resolved for all three isomers. This structure could be simulated using a one-dimensional rigid rotor model. Trends in barriers to internal rotation were in line with previous studies on other toluenes but some noticeable differences were found 2-ABTF shows substantial activity in both the CF₃ and NH₂ torsions indicating a substantial interaction between the two substitutions. The electron withdrawing nature of the CF₃ makes the formation of an intramolecular hydrogen bond possible. For all three isomers considerable activity was observed in torsional transitions which are forbidden by symmetry selection rules.

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This thesis contains the results of studies by single crystal vibrational spectroscopy of several materials. In an introduction the essential facts necessary for an understanding of the construction and nature of crystals in relation to single crystal vibrational spectroscopy are summarised. A review of i.r. reflectance spectroscopy is given as this was the major technique used in this research. A brief description of the Raman process is also given as well as methods of crystal growth used for this work. Single crystal i.r. and Raman spectra for topaz are reported. A complete assignment is given for the v(Si-O) region; at lower frequencies there is a more or less continuous range of modes and any assignments in this regian must be tentative. Some fragmentary data for spodumene are reported. Single crystal i.r. and Raman spectra for AICI3.6H2O are reported and, together with data collected from the deuteriate, enable an assignment to be given. The assignment takes note of normal coordinate analysis calculations, deuteriation shifts, and factor group components, as well as solution data. An assignment for the modes due to water motions is given by comparison with previous assignments for mono-and di-aquated complex ions. Far-i.r. spectra of HgCl2 HgBr2 are reported at both ambient and low temperatures. For HgCl2 the trans- latory modes have been identified from the fundamental modes predicted by theory, all of which have been observed. All the fundamental modes of HgBr2 have been observed and assigned to symmetry species. Far-i.r. spectra of three complex halides with the CsNiCl3 structure are reported at ambient temperature. The results agree well with those reported previously for mulls and an unambiguous assignment is given. Far-i.r. spectra of five square-planar complexes are reported at both ambient and low' temperatures. Complete assignments for K2PtBr4, (NH4)2PtCl4 and (NH4)2PdCl4 ware given for the first time. In the case of K2PtBr4 V4 and V7 are accidentally almost degenerate at ambient temperature. The lattice mode region of the ammonium salts has been assigned; the breadth of the central region of i.r. mulls of these compounds is due to three bands occurring in close proximity. The occurrence of low temperature features in the chlorides has been confirmed, the possible origin of these modes is discussed. A simplified factor group analysis scheme is given for the 80 diperiodic groups which lack periodicity in the third dimension. Examples of the use of the Tables are given. Listings of computer programs used for i.r. reflectance analysis are given in the appendices.

A review is given with over 100 references of equipment for and results obtained in the field of vibrational spectroscopy at high pressures in the period June, 1975 to June, 1977. The device used in this thesis, the Diamond Anvil Cell (DAC), is analysed in detail and redesigned. A full discussion is given of earlier designs. The complex problems that arise in optical coupling of the DAC to i.r. and Raman spectrometers are also studied. Pressure calibration using the R fluorescence lines of Ruby is fully discussed and the problems of low temperature high pressure experiments investigated, and a calibration proposed. Three classes of compound are investigated: (i) organic (benzene), (ii) inorganic molecular (mercuric halides), and (iii) inorganic ionic (CsNiCl3). For benzene the same sample held under hydrostatic pressure in a gasketed DAC was examined by Raman, far-i.r. and mid-i.r. spectroscopy. Spectra of the solid phases of I and II were recorded and evidence for the elusive phase III obtained. The Raman spectra compared well with those obtained by Nicol using a much larger sample in a Drickamer cell whilst the i.r. results are entirely new. HgX2 (X = Cl, Br, I) have been studied in detail up to ca. 40 kbar and almost all known phases characterised by Raman and i.r. spectroscopy and structures proposed for several phases of hitherto unknown structure. In particular the high pressure form of yellow Hgl2 is shown to differ from the yellow high temperature modification. Raman and i.r. spectra of CsNiCl3 at various temperatures and pressures have been obtained and analysed, using compressibility and thermal expansion data determined as part of the study, in terms of anharmonic parameters.

A scheme is presented for a computer program using the Configuration Interaction method. To make the program as flexible as possible, lists of spin-configurations over RHF molecular orbitals are kept. These separate configurations for the alpha and beta spins can be combined to give the total configurations as and when necessary. It is shown how advantage may be taken of the internal bit structure of a computer word so as to store the spin-configurations as a binary pattern, which provides economical storage, and how information can then be extracted from them by means of the computer's logical machine instructions. The Configuration Interaction method is applied to the calculation of magnetic resonance properties. The Electron Spin Resonance hyperfine coupling constants of the [special character omitted]-radicals NH2, BH3-, CH3 and NH3+ and the a-radicals BeOH and BeH are studied using a range of basis sets and allowing various levels of excitations to be included in the CI. Rather more tentative results are presented for the Nuclear Magnetic Resonance coupling constants of CH4, NH3, H2O and HF using only minimal basis sets.

The frequency with which a surfactant monomer enters and leaves a surfactant micelle has been the subject of much discussion. It is possible, using EPR, to measure the frequency with which a paramagnetic molecule changes to a magnetically different environment if that frequency is between 105 and 109 sec-1, or alternatively to state whether the exchange frequency is faster or slower than these limits. If the paramagnetic molecule were also a surfactant, this technique would give information about the exchange frequency between monomer and micelle, since these have magnetically different environments. A series of paramagnetic surfactants (I) was prepared. The EPR spectra of micellar solutions of these surfactants consisted of one broad line due to the micelles, superimposed upon three sharp lines due to the monomeric nitroxide surfactant. This showed that the monomer- micelle exchange frequency was in the slow region. Increasing the temperature increased the width of the monomer lines, and it was initially thought that this was indicative of measurable monomer-micelle exchange. Further experiments produced inconsistent results. In an attempt to understand these results, a theoretical investigation of the linewidth behaviour expected for monomer-aggregate exchange was made, which indicated that under certain conditions the mI = +1 nitroxide lines might broaden more than the mI = 0 line. This would enable one to distinguish monomer-aggregate exchange from Heisenberg spin exchange. Since these linewidth effects were small, an attempt was made, by computer-simulation, to take into account the effect of proton hyperfine structure on the observed linewidth. This attempt was not successful as the proton hyperfine coupling constants were found to decrease with increasing exchange frequency in the region of interest. The problem was further complicated by the presence of pre-micellar aggregates, which seem to be caused by the nitroxide head group and not by the hydrocarbon chains of the surfactant. A final series of experiments showed that the observed linewidth increases were not due to monomer-micelle exchange, but to a combination of monomer-dimer exchange and Heisenberg spin exchange. Thus this EPR technique yields only the information that the monomer-micelle exchange frequency is slower than 105 sec-1. Other EPR experiments involving the nitroxide analogue of an oily soil are described. The physical state of the paramagnetic soil on fabric, the removal of the soil under different conditions, and the re-deposition of the soil are described, as is the construction of a capillary washing chamber, an effective washing-machine simulator which operates in the cavity of an EPR spectrometer and in which these experiments were performed.

Part One of this Thesis describes the vibrational spectra obtained from molecules adsorbed onto surfaces. The Raman spectra of pyridine adsorbed onto Cab-o-Sil, kieselgel and Vycor porous glass are shown and some conclusions about the nature of the surfaces made. The Raman spectra of molybdenum hexacarbonyl adsorbed onto Vycor and of a variety of molecules adsorbed onto nickel, nickel oxide, copper, and copper oxide supported on Vycor are reported. The infra-red spectra of nitric oxide, nitrogen dioxide, oxygen, carbon dioxide, and mixtures thereof adsorbed on to titania (anatase) are reported, as are the spectra of nitric oxide, carbon monoxide, and a mixture thereof adsorbed on to anatase containing molybdenum hexacarbonyl. The surface species formed are discussed. Part Two of this Thesis describes the vibrational spectroscopic study of several minerals as oriented single crystals. Criteria for choosing the minerals studied are discussed, and an outline of the Raman and i.r. reflection techniques given. Members of the apatite group of minerals, (fluorapatite, vanadinite and mimetite), were studied and a full vibrational analysis of fluorapatite given. The related minerals beryl, dioptase and benitoite were studied, and full vibrational analyses of beryl and benitoite are given. The phenomenon of L.O./T.O. splitting as exhibited by benitoite is discussed.

Electron Spin Resonance is used to detect radiolytically produced silver centres in a range of alkali halide:silver halide mixtures. A new silver aggregate electron excess centre is detected in mixtures of NaCl:AgCl containing high [Ag+] and a silver atom species is detected in a KF lattice where it appears to be coordinated asymmetrically to six fluoride ligands. The stability of Ag2+ as a hole centre in halide lattices is demonstrated. Silver centres in irradiated frozen solutions, as studied by ESR, can provide information on the solvation of the parent Ag+ ion. A solvation number of four for Ag+ in methyl cyanide is found and a solvation number of four or six in water seems likely. The spectra associated with other solvents are less informative, but some general conclusions regarding solvation and ion pairing are made. Silver atom-ion aggregates are frequently detected in these systems although aggregates of more than four silver nuclei are not found in any of the solvents studied. NMR results for cation induced shifts in the hydroxyl proton resonance in aqueous and methanolic solutions of a range -d10 metal cations support the view that the solvation number for Ag+ in these media is between four and six. An ESR study of radiation damage in a range of inorganic nitrates reveals a new paramagnetic nitrogen oxide or oxy-ion. So far unidentified, it appears to be similar to, but distinctly different from, NO3. Electron capture is studied in -d10 metal nitrates where there is a subtle balance between capture at cation and at anion sites; the paramagnetic centres in these nitrates often exhibit superhyperfine structure that can be linked to the crystal structures. The radiolysis of dinitrogentetroxide and the formation of N2O4+ and N2O4- is also studied.

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