In-situ spectroscopy: gas mixture analysis using a simplified multi-pass capillary cell and optical considerations in dualpulse laser-induced breakdown spectroscopy analysis of bulk aqueous solutions

This thesis describes two methods investigated for their uses as tools for in-situ spectroscopy. As knowledge in the Chemical Sciences as well as technology progress, scientific questions are encountered that require analyses to be performed in-situ due to concerns that sampling and sample preparation may not provide the most accurate information. The two methods described herein will be an in-situ gas sensor using Raman Spectroscopy and considerations for a laser-induced breakdown spectroscopic method geared towards in-situ analysis of hydrothermal vents.;Chapter 1 will describe a novel, yet simple gas sensor that utilizes a fiber-optic Raman sensor coupled to a simplified multi-pass capillary cell (MCC). Improvements in the cleaning methods of the capillary tubes used to create the MCCs have resulted in higher quality silver coatings. Coupled with a filtered 24 1 fiber optical probe has resulted in detection limits for CO 2, O2, n-butane, CH4 and H2 that are comparable to those in the literature using more complicated systems.;Chapter 2 will focus on optical considerations for dual-pulse laser-induced breakdown spectroscopy analysis of bulk solutions using a collinear optical geometry. Shadowgraphic imaging was used to observe the vapor bubbles that resulted from the laser-induced plasma formed by an achromatic doublet that reduces spherical aberrations compared to two conventionally used spherical optics, a bi- and plano-convex lens. The achromatic doublet produced larger, longer-lived and more reproducible bubbles. The higher power density resulted in a higher frequency of laser pulses resulting in bubbles.