Time-resolved Fourier spectroscopy has been applied to the observation of Rydberg O(I) and O(,2) infrared emission from a pulsed discharge at 0.1 torr. The emission of a 2.5 meter long column through the negative glow was observed with a newly designed discharge apparatus. A computer-controlled interferometer step-servo was developed to enable 100 microsecond time- and 0.12 cm('-1) spectral-resolution capabilities. The Rydberg features were enhanced with respect to those of contaminates by signal processing methods that utilized their individual temporal behavior. Line position determinations of the 7h - 5g, 7g - 5f, 5g - 4f and 6g - 4f O(I) lines have been made to an accuracy of 0.015 cm('-1). Polarization constants of the O(II) core have been deduced from this data. Nine newly observed and four previously observed line-like features have been attributed to Rydberg O(,2).

No Abstract provided / Thesis / Master of Science (MSc)

The theory of Atoms in Molecules is applied to a series of borane molecules. A study of the topological features of the charge density, p(r), yields a quantum mechanical definition of atoms, bonds, and the average properties of atoms within a molecule. Other topological features of the boranes studied include rings and cages, formed by bond paths in p which link the atoms. These bond paths which form rings are bent inward in order to maximize the binding in these electron-deficient molecules. An important result of this analysis is the unambiguous assignment of the connectivity of the boranes. The theory of atoms and molecules allows one to quantum mechanically partition molecules into atomic basins, and calculations of average values for electron count and energies of individual atoms are performed by integration over these basins. Comparisons of atomic properties are performed to determine the transferability of atomic properties across the series. The Laplacian of p, V2p, yields information about sites of electrophilic and nucleophilic attack in molecules. These sites are found to correspond to the positions of critical points in V2p, which are localized to specific atoms in the molecule. The boranes and carboranes are ranked according to their susceptibility to electrophilic and nucleophilic attack, and such reactions with boranes are predicted to be regiospecific. / Thesis / Master of Science (MSc)

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Discussion begins with a brief account of atomic level-pumping and reasons why atomic coherence is typically not considered in cw work on optical interactions. This dissertation is divided into four parts: semiclassical treatments of one-photon electric- dipole atom-field single-mode interactions and multimode interactions, and corresponding treatments for the two-photon interaction. We present the effects of injected atomic coherence on the polarization of the medium, the slowly varying envelope wave equation, the single- and multiwave mixing coefficients, and weak field propagation in a homogeneously broadened two-level medium. Spatial and temporal phase matching of the injected coherence to a field mode is crucial throughout, since the field may not be able to remain in phase with the induced and injected polarizations. One-photon injected coherence contributes directly to the polarization at the atomic resonance frequency. The perfectly phase-matched case leads to a linear superposition of an exponentially decaying field (Beer's law) and a constant field driven by the injected coherence. The interaction of an injected coherence with a detuned field produces frequency-symmetric sidebands about the pump field polarization. The sideband spacing equals the atom-field detuning. To probe the injected coherence we inject a weak resonant field. The resulting three-wave mixing leads to multiwave mixing coefficients that are unaffected to first-order in the weak sidemodes, but the injected coherence adds inhomogeneous terms to the coupled-mode equations. For both single- and multimode interactions the injected coherence does not affect the exponential growth/decay of the sidemodes, but it supports a weak field that may propagate if properly phase matched. For two-photon media the injected coherence requires at least one field interaction in order to produce a polarization, which then appears in the single- and multiwave mixing coefficients. The exponential growth/decay rate is modified by the injected coherence. For a centrally-tuned pump the injected coherence contributes the standard multiwave mixing terms as well as additional effects. Four-wave mixing is discussed as a means of relaxing the spatial phase matching constraint on the injected coherence.

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The Interacting Boson Model (IBM) has been very successful in describing the collective properties of nuclei. This work concerns two systematic applications of the model, one involving configuration mixing, and the other involving octupole bands. The even isotopes of mercury are of special interest because of the coexistence of two sets of bands, of very different character, in the lighter nuclei. The neutron-proton IBM (IBM-2) with configuration mixing provides a good description, both of states built on the normal ground state and of those associated with a proton pair excitation across the Z = 82 closed-shell gap. Eleven isotopes are studied, ranging from the middle of the neutron shell to very near the doubly closed shell at ²⁰⁸Pb. The same Hamiltonian is used for all the nuclei studied, with parameters which are constant or smoothly varying. There have been extensive IBM studies of low-lying positive parity bands, which are based on the ground state and the quadrupole degree of freedom. The present work comprises the first systematic IBM study of the corresponding negative parity bands, which are based on the octupole degree of freedom. In this model, an f boson is coupled to a positive parity core, described by the usual s and d bosons. This is done within the original IBM framework, called IBM-1, which does not include separate neutron and proton degrees of freedom. The IBM octupole model is presented and the phenomenology is explored, both for the full model, and for the SU(3) limit of the model. Calculated energy spectra and B(E3) transition rates are presented for nine deformed rare-earth nuclei. There is good agreement with available experimental data for these nuclei. It is shown that nuclei for which the two lowest octupole bands are K = 2 and 0 cannot be described within the present model. In this case, it appears that separate neutron and proton octupole degrees of freedom are necessary. The exchange term in the Hamiltonian is shown to arise from a neutron-proton octupole-octupole interaction. A consistent octupole model is developed and successfully applied to the nucleus ¹⁶⁸Er.

In this thesis we study various dissipative processes that are associated with the flow of an atomic Bose-Einstein condensate at zero temperature. In particular, we investigate the effect of a weak correlated disorder potential on the collective dipole motion of a harmonically-confined elongated condensate. By using an extension of the Harmonic Potential Theorem, we demonstrate that the dynamics of the system can be described equivalently in terms of a disorder potential oscillating relative to a stationary condensate. This latter point of view allows the application of linear response theory to determine the drag force experienced by the condensate and to evaluate the damping rate of the centre of mass oscillation. The density response function for the elongated condensate is determined with a new local density approximation that takes into account the tight radial confinement of the atomic cloud. Our linear response theory reveals the detailed dependence of the damping rate on various system parameters. A comparison with available experimental data is only partially successful and points to the need for additional experiments. In addition to disorder induced dissipation, we also consider a variety of other problems that can be addressed by means of linear response theory. For example, we study momentum transferred to a condensate by a Bragg pulse and the energy absorption of a gas in an optical lattice that is parametrically modulated in different ways. All of these applications demonstrate the utility of linear response theory in describing the dynamics of Bose-condensed systems which are subjected to weak perturbations. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-04-26 10:54:11.915