Modifications have been made to the programs used at Edinburgh for the analysis of the nuclear magnetic resonance spectra of molecules dissolved in liquid crystal solvents. In addition, an investigation has been made into the use of molecular mechanics force fields to calculate vibrational corrections to diffraction and spectroscopic data, necessary if a structural analysis is to be carried out using data from diverse sources. The technique of combined analysis has been applied to the structural determination of the three isomeric difluorobenzenes and to 2-chloropyrimidine, 3,6-dichloropyridazine and 2,6-dichloropyrazine. Data from electron diffraction, microwave spectroscopy and liquid crystal nuclear magnetic resonance spectroscopy have been used in these analyses, with varying degrees of success. The geometries obtained are largely consistent with results obtained for molecules of the same class.

The NA48 experiment is a fixed target experiment on the Super Proton Synchrotron accelerator at CERN. The aim of the experiment is to investigate direct CP violation in the neutral kaon system by measuring the parameter <i>Re</i>(Î'/Î) to an accuracy of 2 x 10^-4. In 1998 the NA48 experiment took 14 weeks of data for this measurement. This thesis describes a method for determining <i>Re</i>(Î'/Î) and the systematic studies of the measurement. The result of my analysis is: <i>Re</i>(Î'/Î) = (12.6±2.8±3.7) x 10^-4 where the first error is statistical and the second error is systematic.

The Rydberg and ion-pair states of Cl<SUB>2</SUB>, Br<SUB>2</SUB>, I<SUB>2</SUB>, ICl and IBr have been studied using a range of laser-based spectroscopic techniques, in the vacuum-ultraviolet (VUV) energy region. The [2+1] resonance enhanced multiphoton ionization (REMPI) spectrum of Br<SUB>2</SUB> has been re-examined in the region 56 000-86 000 cm<SUP>-1</SUP>. Rydberg series, previously assigned to components of the <I>ns</I> Rydberg states have been reassigned to components of the (<I>n</I>-2)d Rydberg states, for <I>n</I>≥6. The lowest 5s Rydberg state components on each ionic core remain unchanged, based on energetic considerations. The Ω values of the Rydberg states were deduced from rotational band contour analysis and from intensity ratios under linear and circular polarization. A propensity rule for assignments based on two Ω components with significant singlet character (Ω=0 and Ω=2), on each ionic core, was determined in terms of the microconfigurations for the Hund's case (c) states. As an exception, triplet components (Ω=1) are also observed for the lowest <I>n</I> in a particular Rydberg series (<I>n</I>=4 for the d-series in Br<SUB>2</SUB>). This reassignment prompted a reinvestigation of the one- and two-photon spectra of the halogen and interhalogen molecules, Cl<SUB>2</SUB> I<SUB>2 </SUB>, ICl and IBr in terms of the propensity rules developed for Br<SUB>2</SUB>. The one-photon spectra of I<SUB>2</SUB> and ICl were recorded using VUV laser radiation, generated by four-wave mixing in Kr gas. Ion-pair formation (X<SUP>+</SUP>+Y<SUP>-</SUP>) <I>via </I>predissociation of Rydberg states was observed from all states seen in the one-photon absorption spectrum of each molecule. Spectra were recorded from the ion-pair threshold up to the ionization limit. The field-lowering effect induced by the high electric field in the extraction region of the time-of-flight mass spectrometer was investigated with I<SUB>2</SUB>. Predissociation in I<SUB>2</SUB> and ICl is discussed in terms of a two-electron exchange mechanism connecting the electronic configurations of the Rydberg and ion-pair states.

Oxygen atom transfer reactions in a series of early transition metal complexes in both solution and solid state were investigated, with a particular interest in O-atom transfer processes from bonded NO<SUB>x</SUB> (x= 1,2,3) ligands to adjacent carbonyl groups. The main objective was the synthesis and characterisation of new mixed CO/NO<SUB>2</SUB><SUP>-</SUP> species. In Chapter 1 a general review of oxygen atom transfer reactions involving CO and NO<SUB>x</SUB> is given. Chapter 2 presents the results gained from reactions of M<SUB>2</SUB>(CO)<SUB>10</SUB>, ClM(CO)<SUB>5</SUB> and several other carbonyl halides {M=Mn, Re} with [PPN][NO<SUB>2</SUB>]/[PPh<SUB>4</SUB>][NO<SUB>2</SUB>]. Chemical activation by (CH<SUB>3</SUB>)<SUB>3</SUB>NO prior to interaction with [PPN][NO<SUB>2</SUB>]/PPh<SUB>4</SUB>][NO<SUB>2</SUB>] has also been investigated. Complexes isolated and characterised by IR spectroscopy and X-ray diffraction include [(OC)<SUB>3</SUB>Mn(μ<SUB>2</SUB>-<I>NO</I>(O))<SUB>2</SUB>(μ<SUB>2</SUB>-O(NO))Mn(μ<SUB>2</SUB>-<I>NO</I>(O))<SUB>2</SUB>(μ<SUB>2</SUB>-O(NO))Mn(CO)<SUB>3</SUB>](PPN)<SUB>2</SUB>, {[CIRe(CO)<SUB>3</SUB>(<I>NO<SUB>2</SUB></I>)<SUB>2</SUB>]C1[(CH<SUB>3</SUB>)<SUB>3</SUB>NCH<SUB>2</SUB>C1]<SUB>3</SUB>} and [Re(CO)<SUB>3</SUB>(ONO)<SUB>3</SUB>](PPN)<SUB>2</SUB>. Compounds such as Mn<SUB>2</SUB>(CO)<SUB>8</SUB>(PPh<SUB>3</SUB>)<SUB>2</SUB>, [Mn(CO)<SUB>4</SUB>C1(PPh<SUB>3</SUB>)] and [<I>trans</I>-Mn(CO)<SUB>3</SUB>C1(PPh<SUB>3</SUB>)<SUB>2</SUB>] substituted in part by tertiary phosphines have been tested towards their reactivity with [PPN][NO<SUB>2</SUB>]/[PPh<SUB>4</SUB>][NO<SUB>2</SUB>]. Reaction pathways are discussed on the basis of detailed IR spectroscopy studies. In Chapter 2.3. reactions of M(CO)<SUB>6</SUB>, [M(CO)<SUB>5</SUB>C1](Et<SUB>4</SUB>) {M= Cr, Mo and W} and [(OC)<SUB>3</SUB>Mo(μ<SUB>2</SUB>-C1)<SUB>3</SUB>Mo(CO)<SUB>3</SUB>](NEt<SUB>4</SUB>)<SUB>2</SUB> with [PPN][NO<SUB>2</SUB>]/[PPh<SUB>4</SUB>](NO<SUB>2</SUB>] are presented. Mixed CO/NO<SUB>2</SUB> species were prepared for all three metals and structurally characterised in the solid state in form of [M(CO)<SUB>5</SUB>(<I>NO<SUB>2</SUB></I>)](PPh<SUB>4</SUB>) {M=Cr and W}. Mixed CO/NO complexes of Manganese (2.1.3.) and Chromium (2.3.2.) have been synthesised and their reactions with O<SUB>2</SUB> investigated. Oxidation of the nitrosyl ligands was observed in both cases and possible reaction mechanisms are presented.

The phenomenon of collision-induced electronic energy transfer in selectively excited diatomic radicals has been investigated experimentally. Direct laser excitation of initial rovibronic states and dispersed, temporally-resolved fluorescence analysis of both parent <I>and</I> collisionally populated levels has allowed the collisional encounter to be quantified at a <I>state-specific </I>level. Theoretical modelling of these results allows the form of the potential energy surfaces which control the dynamics to be established. In an extended series of experiments, collision-induced C<SUP>2</SUP>Δ-B<SUP>2</SUP>Σ<SUP>+</SUP> transfer in the SiF radical has been investigated. It was observed that the product B<SUP>2</SUP>Σ<SUP>+ </SUP>state vibrational distributions were well correlated with the Frank-Condon overlap between vibronic wavefunctions of the two states. Dominant channels were found to involve Δ<I>v</I>=0, which corresponds to the energy defect of ~5000 cm<SUP>-1</SUP>. Rotationally resolved investigation of the C<SUP>2</SUP>Δ, <I>v</I>=0→B<SUP>2</SUP>Σ<SUP>+</SUP>, <I>v</I>'=0 channel revealed a significant fraction of this energy to be released as product state rotation. A limiting impulsive model of the energy release reproduced the main features of the observed behaviour. Polarisation resolved investigation of the transfer event revealed significant depolarisation of the product B<SUP>2</SUP>Σ<SUP>+</SUP> state compared to the initial C<SUP>2</SUP>Δ state. This observation was rationalised within two dynamically distinct models of rotational energy transfer. It is believed that all these observations may be explained by the valence-Rydberg nature of the electronic states involved. In a related set of experiments, novel measurements of collision-induced transfer between the A<SUP>2</SUP>Δ and B<SUP>2</SUP>Σ<SUP>-</SUP> states of the CH radical have been obtained.

This thesis describes a lattice study of matrix elements relevant to the semi-leptonic decay of B mesons. The simulation was performed on two lattices, the first with a volume of 16<SUP>3</SUP> x 48 at <I>β</I> = 6.0 and the second with a volume of 24<SUP>3</SUP> x 48 at <I>β </I>= 6.2. Both lattices employ on <I>O</I>(<I>a</I>) non-perturbatively improved fermion action in the quenched approximation. The thesis describes fully the theoretical tools required to analyse such a process on the lattice, in particular Lattice QCD and Heavy Quark Effective Theory. The two form factors relevant to the decay <I>B → Dlv </I>are extracted using these theoretical tools and their dependence on the various kinematical quantities is studied. The Isgur Wise function is obtained from the heavy quark limit of these form factors and its slope is extracted. From a comparison of this Isgur Wise function and the experimental analysis of the decay, the Cabbibo-Kobayashi-Maskawa matrix element <I>V<SUB>cb</SUB></I> is obtained.

No description available.

No description available.

The electronic spectroscopy of the hydrogen halides has been investigated using laser multiphoton excitation techniques; the (2+ 1)REMPI spectra of HBr, DBr, and HI in the two-photon energy range 76000 - 83000 cm<SUP>-1</SUP> and 67000 - 73000 cm<SUP>-1</SUP>, the fluorescence excitation spectra of DCl and HI, and the fluorescence emission from ion-pair and Rydberg states in HCl, DCl, and HI have been recorded. New transitions were observed in the (2+ 1)REMPI spectra of HBr, DBr, and HI and a previously reported transition in HBr was reassigned. The fluorescence spectra recorded from a number of 0<SUP></SUP>+ Rydberg states in HCl, DCl, and HI showed structure characteristic of the ion-pair state which indicates that these states vibronically couple with the ion-pair state. In HCl and DCl the g<SUP>3Σ-</SUP> (0<SUP></SUP>+ ) and E<SUP>1Σ</SUP>+ (0<SUP></SUP>+ ) Rydberg states are coupled to the ion-pair state while in HI the E<SUP>1Σ</SUP>+ (0<SUP></SUP>+ ) and j<SUP>3Σ-</SUP> (0<SUP></SUP>+ ) Rydberg states are coupled to the ion-pair state. Numerical modelling techniques were used in the analysis of both the previously reported spectra and the experimental results presented herein. The excited states and the coupling between them were modelled in both the diabatic and adiabatic representations. The vibrational energy levels and rotational constants have been calculated and the absorption and fluorescence spectra of HCl and DCl have been simulated. The comparison of observed and calculated data has been used to refine the model of the potential curves and the coupling between the states. The greatest amount of information was available for HCl and so the work reported here has concentrated on this molecule and DCl.

(e,2e) spectroscopy is a versatile tool to investigate the collision dynamics taking place in electron impact ionisation of atoms and molecules as it employs a kinematically complete view of the scattering process. (e,2e) measurements on He and H2 have been carried out from the coplanar to the perpendicular geometry at various impact energies, and these results are compared and discussed. Results for the atomic targets He, Ar and Xe and the molecular targets H2, N2 and CO2 are also presented from measurements in the perpendicular geometry and these are compared. The Ib1 molecular orbital of H20 has been studied at low to intermediate energies in a coplanar symmetric and asymmetric geometry. Where available the experimental data have been compared to theoretical calculations of other research groups located in the USA. A new coincidence spectrometer has been designed, assembled and commissioned which incorporates a pulsed, supersonic beam expansion as well as a continuous, effusive beam expansion. Measurements using supersonically expanded He and H2 demonstrated the feasibility of the new coincidence spectrometer for (e,2e) studies. The supersonic gas expansion provides molecular targets in their ground ro-vibrational states. This spectrometer allows the first steps towards the development of molecular alignment within the target beam. The alignment of diatomic molecules in the experiments would open up a new range of (e,2e) measurements with far-reaching implications for the investigation of collision dynamics from molecules.