Development of Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) and application to laboratory and field measurements of trace gases and aerosols

Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) can measure gases and aerosols relevant in the atmosphere. Human activity and natural processes contribute constituents to the atmosphere that effect air quality, health and climate. Primary pollutants and secondary products of the chemistry (O3, aerosol) of these pollutants have impacts on human health (photochemical smog and aerosols increase mortality and morbidity rates), quality of life (visibility) and global climate. CE-DOAS utilizes a high finesse cavity consisting of a pair of highly reflective mirrors between which light makes many passes before leaking out of the cavity and being detected to realize long path lengths (5-30 kilometers) over a small cavity length (1m) leading to enhanced sensitivity. The work is presented as follows: (a) Design, construction and characterization of CE-DOAS as well as data analysis development; (b) Temperature dependent measurements of O4 cross-sections in the ultra-violet and visible wavelength range; (c) Measurements of Rayleigh Scattering cross-sections at UV and visible wavelengths; (d) Instrument inter-comparisons of CE-DOAS with other techniques; (e) mechanistic studies of the chemistry of isoprene oxidation; and (f) deployment of CE-DOAS for field measurements