| Considerable research has been done on the analysis of single particles in Laser Induced Breakdown Spectroscopy (LIBS); however, plasmas formed in gases or aerosols at atmospheric pressure have not been sufficiently characterized. It has previously been determined that the introduction of particles into a gas plasma does not significantly change parameters such as plasma excitation temperature. This infers that once fundamental parameters of an air plasma are determined, then these same parameters would apply to a plasma encompassing a single particle. Curve of growth (COG) methodology provides information regarding spectral broadening processes for absorption and emission measurements in flames and has recently been implemented for the resonance transition of chromium in LIBS analysis of stainless steel standards. In this work the curve of growth methodology was applied to a plasma formed in a gaseous sample, a mix of carbon dioxide, CO2, and argon, and the curves were generated using the non-resonance transitions of C(I), at 193.0905 nm and 247.8561. These transitions were selected because they undergo self absorption and emit radiation in the ultraviolet and visible region, the region of detection for typical LIBS instrumentation. The applicability of this theory to LIBS of gas plasmas was assessed. The experimental calibration plots plateaued and decreased, not allowing the broadening effects to be elicited through the curve of growth method. Diagnosis of the cause behind the unusual calibration plots was performed using additional experiments examining the oxygen emission, and examining the line broadening of both of these transitions. The dissociation fraction of the CO2 changed as more CO2 was added. Broadening processes in the plasma were able to be determined and the instrumental requirements to utilize COG theory were ascertained.; The threat of additional terrorist attacks with biological agents such as anthrax has placed detection of bioaerosols and specifically bacillus spores at the forefront of LIBS applications. The possibility of using LIBS for detection of single spores was explored theoretically and the analysis of single spores of Bacillus licheniformis was performed with an intensified charge couple device (iCCD). Limitations of the method for single spore analysis were also determined. |
