Ultrasensitive Detection of Aerosol Precursors Including Ammonia

78830 The Department of Energy requires improved measurement techniques to quantify trace gas species in the atmosphere, in order to achieve further understanding of the formation of aerosols and their role in climate change. This project will combine a novel, ultra-sensitive, photo-acoustic detection technique with a high power, widely tunable mid-infrared laser source to enable rapid, sub-part-per-billion detection of a wide range of species including aerosol precursors such as ammonia and nitric acid. Key advantages of the technique are the ability to measure multiple gas species, the small size of the detector unit, and the absence of any requirement for cryogenic cooling in the system. In Phase I, a mid-infrared optical parametric oscillator (OPO) with an output power of 1 Watt will be developed as the excitation source for quartz-enhanced photo-acoustic spectroscopic (QEPAS) detection of multiple trace gas species. Direct absorption spectra of a variety of species will be acquired, and real-time concentration measurements of a calibrated trace gas sample will be performed using the QEPAS technique. Finally, an assessment of the technique in terms of its ultimate sensitivity and range of species detectable will be made, leading to a design for a Phase II multi-species detection system. Commercial Applications and Other Benefits as described by the awardee: The new system should provide a detection capability for wide variety of species with high sensitivity and should contribute to a wide range of industrial and scientific problems, including detection of impurities in gases used in semiconductor fabrication, measurement of hydrocarbon gas leaks in the petrochemical industry, studies of pollution sources and of aerosol formation for investigation of climate change.