The Fabry-Pérot interferometer (FPI) was investigated as a potential tool for determining stellar elemental abundances. The FPI is a tunable narrow-band filter that makes it possible to obtain hundreds of stellar spectra simultaneously without the overhead associated with other multi-object spectroscopy techniques. This thesis used simulations and previously acquired data to investigate the FPI and develop data reduction techniques. Using observations of a CaII spectral line, an algorithm was created for fitting a Voigt profile to the spectrum segments. The values for radial velocity & equivalent width were compared to the values found by the group who supplied the data and found to agree well for the radial velocity values but there was some definite scatter in the equivalent width. These differences are attributed to different placement of the continuum level in the spectra. This curve-fitting script was modified to allow the fitting of synthetic spectra to simulated data. In this way it was possible to investigate how precise the abundance determination will be using the Robert Stobie Spectrograph's FPI mode. Large simulations showed that it will be possible to determine abundances to uncertainties of ±0.1 dex. This is an excellent result and should mean that future work using the FPI will give the results desired for large-scale s-process elemental abundance determination in globular cluster stars.

No description available.

This thesis is concerned with the development of ab-initio molecular dynamics (AIMD) using density functional theory, and its application to simple diatomics and small sodium clusters. The approach follows Car and Parrinello and the local spin density (LSD) approximation is taken as a starting point for the description of the electronic states in these systems. An improvement to LSD by correcting for the spurious self-interaction terms (SIC), as proposed by Perdew and Zunger, and the way in which this can be implemented is considered. The SIC corrected LSD is tested on simple diatomic molecules, and is shown, especially for the case of H₂, to significantly improve on the LSD description of the potential energy curve and the spin pairing/unpairing transition. LSD and SIC are then compared for small sodium clusters, for which the geometries, binding energies, and polarizabilities are determined, as well as vibrational frequencies for two clusters. Conclusions are hampered by the lack of experimental data, and uncertainties due to the pseudopotential. However SIC gives a more accurate description of the binding energies, and the unique SIC orbitals allow a description of the bonding which accurately predicts the relative stabilities of the clusters and rationalises their geometries. The problems of breakdown of the Car-Parrinello (CP) method due to "nonadiabatic" effects is considered and it is shown that the problems arising during bond formation and bond breaking, as illustrated by the case of Na₂, can largely be overcome by applying an external thermostat to the fake degrees of freedom. This method is then tested using the dynamics of small sodium clusters. In particular the dynamics of the pseudorotation of Na₃ is studied and it is shown that the mechanism and information about the kinetics can be determined. Finally other methods for improving upon LSD are considered. It is shown that gradient corrections using a plane wave basis set have inherent problems in implementation. Implementation of the exact Hartree-Fock exchange is considered, and this in conjunction with a form of self-interaction correction on the correlation is shown give very accurate results for simple diatomics which are cheaper than using full configuration interaction methods.

No description available.

The Fabry-Pérot interferometer (FPI) was investigated as a potential tool for determining stellar elemental abundances. The FPI is a tunable narrow-band filter that makes it possible to obtain hundreds of stellar spectra simultaneously without the overhead associated with other multi-object spectroscopy techniques. This thesis used simulations and previously acquired data to investigate the FPI and develop data reduction techniques. Using observations of a CaII spectral line, an algorithm was created for fitting a Voigt profile to the spectrum segments. The values for radial velocity & equivalent width were compared to the values found by the group who supplied the data and found to agree well for the radial velocity values but there was some definite scatter in the equivalent width. These differences are attributed to different placement of the continuum level in the spectra. This curve-fitting script was modified to allow the fitting of synthetic spectra to simulated data. In this way it was possible to investigate how precise the abundance determination will be using the Robert Stobie Spectrograph's FPI mode. Large simulations showed that it will be possible to determine abundances to uncertainties of ±0.1 dex. This is an excellent result and should mean that future work using the FPI will give the results desired for large-scale s-process elemental abundance determination in globular cluster stars.

Thesis (M.Eng.). / Written for the Dept. of Chemical Engineering. Title from title page of PDF (viewed 2008/03/12). Includes bibliographical references.

Thesis (M.Eng.). / Written for the Dept. of Chemical Engineering. Title from title page of PDF (viewed 2008/04/12). Includes bibliographical references.

Thesis (Ph.D.)--York University, 2009. Graduate Programme in Physics & Astronomy. / Typescript. Includes bibliographical references (leaves 179-198). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR51495

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007. / Whetten, Robert, Committee Member ; Wang, Z.L., Committee Member ; Perry, Joe, Committee Member ; El-Sayed, Mostafa A., Committee Chair ; Orlando, Thomas, Committee Member.

Proefschrift Universiteit van Amsterdam. / Met samenvatting in het Nederlands.