Title

Optical parametric oscillator-based lasers for analytical atomic spectrometry: Laser excited atomic fluorescence; resonant laser ablation-atomic emission; and laser atomic absorption

Date of Completion

January 1999

Keywords

Chemistry, Analytical|Engineering, Electronics and Electrical

Degree

Ph.D.

Abstract

This dissertation describes some applications of an optical parametric oscillator (OPO) laser in analytical atomic spectrometry. New types of tunable solid-state lasers are reviewed, in Chapter 2, with respect to their principles and characteristic parameters for analytical atomic spectral applications. Then, in Chapter 3, a new commercial OPO laser system is described based on an extraordinary resonance design and experimental results demonstrate its usefulness for the applications in atomic spectrometry. It had a wide tuning range of 225–1680 nm with a narrow spectral linewidth of better than 0.1 cm−1 in the visible spectrum, with high output energy. The slew-scan and continuous scan speeds of the laser were up to 2.5 nm/s and 0.25 nm/s, respectively. A simple, sensitive, and fast method for Sequential Multielement Laser Excited Atomic Fluorescence Spectrometric (LEAFS) analysis of coal for lithium, sodium and strontium was realized by use of the rapid slew-scan speed of the optical parametric oscillator laser. In Chapter 4, the same OPO laser was further used in electrothermal atomization (ETA) LEAFS for the determination of lead in samples of paint by slurry sampling. The high sensitivity and wide linear calibration range of ETA-LEAFS have made multiple dilutions of samples unnecessary, and allowed the analysis of samples with a wide range of analyte concentration. ^ Chapter 5 was devoted to resonant laser ablation (RLA) of molybdenum from a standard steel sample into a microwave induced plasma (ICP) for detection by atomic emission. Compared to conventional non-resonant ablation, the RLA signals were enhanced by factors of greater than five, and the resultant spectra were simpler, which may result in reduced spectral interferences in real sample analysis. Based on the experimental observations, some possible mechanisms of RLA were proposed to begin the process to better understand and make use of RLA. ^ Finally, Chapter 6 describes a preliminary study of OPO Laser Atomic Absorption Spectrometry (OPO-LAAS). Results are presented that illustrate saturation broadening of the atomic profile of sodium, and the linear range of the calibration curves at the center and wings of the atomic spectral profile. In addition, possible applications of OPO-LAAS are discussed. ^