Date of Award

8-2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Christian G. Parigger

Committee Members

Lloyd M. Davis, Horace W. Crater, Trevor M. Moeller

Abstract

The goal of this research is to use optical emission spectroscopy to investigate the processes occurring subsequent to laser ablation of a titanium sample. Laser-induced breakdown spectroscopy provides a procedure for atomic and molecular identification for particular constituents of a laser-induced plasma. Atomic spectral line shapes provide a diagnostic tool for characterizing laser induced plasma, particularly within the first hundreds of nanoseconds. Molecular recombination and/or excitation of selected molecules can lead to simultaneous detection of atomic and molecular species via spectral analysis. Nonlinear fitting of synthetic molecular spectra, calculated via diatomic quantum theory, provides tools for identification, temperature measurement, and further analysis of the diatomic molecules present. By computing accurate line strength values for the TiO molecule, synthetic spectra for the TiO transitions are used to analyze plasma emissions at delay times within the first hundreds of microseconds. In obtaining and analyzing results, numerical methods are implemented. Specifically, use of a Monte-Carlo simulation is studied, as a tool for error analysis. The resulting analysis characterizes the temperature and electron density as a function of time within the first hundreds of nanoseconds. Investigations of TiO spectral transitions along the height of the ablation plume, at time delays of tens of microseconds, reveal two distinct luminescent regions within the plasma with starkly different temperatures.

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