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Abstract Internal rotation in symmetric top molecules offers an excellent opportunity to investigate large amplitude motion in a relatively simple intramolecular environment. Due to specific symmetry characteristics of a symmetric top molecular frame, the internal rotation degree of freedom is in the zeroth order approximation separable from the small amplitude vibrations and the overall rotation, thus enabling to characterize the vibrational-torsional-rotational energy structure with a relatively simple Hamiltonian. Lessons from symmetric internal rotor studies may be applied to more complex systems, such as asymmetric internal rotors and macromolecules. This thesis deals with internal rotation in CH3SiH3, CH3SiD3, CH3CF3 which have become a prototype of symmetric internal rotors. The thesis presents high resolution vibration-torsion-rotation spectra and detailed analysis of these molecules. Particular attention is focused on torsion-mediated interactions, such as Coriolis-type interactions and Fermi-type interactions, coupling the internal rotation and the small amplitude vibrational motion. The studies show that the expansion of the data to the small amplitude vibrations and inclusion of the torsion-mediated interactions play a crucial role in order to obtain an appropriate characterization of the vibrational-torsional-rotational energy level structure and physically meaningful molecular parameters.

The E01-011 experiment at Jefferson Laboratory (JLab) studied light-to-medium mass Lambda hypernuclei via the (e,e'K+) electroproduction reaction. Precise measurement of hypernuclear ground state masses and excitation energies provides information about the nature of hyperon-nucleon interactions. Until recently, hypernuclei were studied at accelerator facilities with intense pi+ and K- meson beams. The poor quality of these beams limited the resolution of the hypernuclear excitation energy spectra to about 1.5 MeV (FWHM). This resolution is not sufficient for resolving the rich structure observed in the excitation spectra. By using a high quality electron beam and employing a new high resolution spectrometer system, this study aims to improve the resolution to a few hundred keV with an absolute precision of about 100 keV for excitation energies. In this work the high-resolution excitation spectra of 12B-Lambda, 7He-Lambda, and 28Al-Lambda hypernuclei are presented. In an attempt to emphasize the presence of the core-excited states we introduced a novel likelihood approach to particle identification (PID) to serve as an alternative to the commonly used standard hard-cut PID. The new method resulted in almost identical missing mass spectra as obtained by the standard approach. An energy resolution of approximately 400-500 keV (FWHM) has been achieved, an unprecedented value in hypernuclear reaction spectroscopy. For 12B-Lambda the core-excited configuration has been clearly observed with significant statistics. The embedded Lambda hyperon increases the excitation energies of the 11B nuclear core by 0.5-1 MeV. The 7He-Lambda spectrum has been observed with significant statistics for the first time. The ground state is bound deeper by roughly 400 keV than currently predicted by theory. Indication for the core-excited doublet, which is unbound in the core itself, is observed. The measurement of 28Al-Lambda provides the first study of a d-shell hypernucleus with sub-MeV resolution. Discrepancies of up to 2 MeV between measured and theoretically predicted binding energies are found. Similar disagreement exists when comparing to the 28Si-Lambda mirror hypernucleus. Also the core-excited structure observed between the major s-, p- and d-shell Lambda orbits is not consistent with the available theoretical calculations. In conclusion, the discrepancies found in this study will provide valuable input for the further development of theoretical models.

<p>Here presents the studies of polymerization kinetics and crosslinking efficiency of nm-resolution striped phases on surface, which depends on lengths of alkyl segments and headgroup chemistry. While fluorescence readouts offer the overall efficiencies of polymerization and crosslinking transfer, SPM measurements reveal molecular details accounting for reactivity differences. Additionally, this research also demonstrates the utilization of primary amines striped phases on soft materials, achieving post-functionalization and specific  adsorption of nanocrystals, highlighting the versatile applications of this nm-scale chemistry boundary.</p>

WR 25 is a colliding-wind binary star system comprising a very massive O2.5If∗/WN6 primary and an O-star secondary in an eccentric orbit with a 208 day period. These hot stars have strong, highly supersonic winds that interact to form a bright X-ray source from wind-collision shocks whose conditions change with stellar separation. Different views through the winds of Wolf-Rayet and O stars are afforded with orbital phase as the stars move about their orbits, allowing for exploration of wind structure in ways not easy or even possible for single stars. We have analyzed an on-axis Chandra/HETGS spectrum of WR 25 obtained shortly before periastron when the X-rays emanating from the system are the brightest. From the on-axis observations, we constrain the line fluxes, centroids, and widths of various emission lines, including He triplets of Si xiii and Mg xi. We have also been able to include several serendipitous off-axis HETG spectra from the archive and study their flux variation with phase. This is the first report on high-resolution spectral studies of WR 25 in X-rays.

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<p> High resolution measurements of the far-infrared absorption spectra due to a number of substitutional impurities in KBr and KCl are presented. Several Van Hove singularities of the phonon spectrum of the host lattice are directly observed and found to shift to higher frequencies as the impurity concentration is increased. The first direct experimental evidence for the change of shape or metamorphism of singularities is also presented. The experimental spectra are compared with numerical calculations based on the ordinary shell model for the defect together with phonon data obtained from inelastic neutron scattering experiments. Agreement between experiment and calculation is generally good when impurity resonant modes are absent.</p> / Thesis / Doctor of Philosophy (PhD)

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This thesis addresses the design of multiple description lattice vector quantizer (MDLVQ) with a general number L of descriptions, L >= 3. In the previous work on MDLVQ with L>= 3, once the central and side lattice codebooks are fixed, the decoding quality is determined for all numbers k of received descriptions. Therefore, it is not possible to achieve tradeoffs between the quality of reconstruction for different values of k, 1<= k <= L-1. In order to overcome the above drawback, we propose two flexible MDLVQ schemes for L >= 3. Our first design employs a different reconstruction method than in prior work and a heuristic index assignment algorithm, which uses L-2 parameters to control the distortions for 2 <= k <= L-1. Experimental results for the cases L=3 and L=4 show that significant tradeoffs are achieved by controlling the parameters mentioned above. Our second design is based on a structured index assignment. We start with the case L=3 and then generalize the index assignment to any L >= 3. The structured index assignment is able to control the tradeoff by adjusting the sizes of some L-1 subsets of side lattice points. Another important contribution of the thesis is the derivation of analytical expressions of the distortions for the structured index assignment, under the high resolution assumption. These expressions show that a wide range of distortion values can be achieved. / Thesis / Master of Applied Science (MASc)