Applications of optical cavity techniques to problems in atmospheric chemistry and spectroscopy

Abstract

Trace gases in the atm. have a profound impact on Earth, influencing air quality and climate. Advances in laser spectroscopy have allowed us to gain deeper insights into the phys. and chem. processes of these mols., through both lab. and in situ measurements. Our work has exploited the high sensitivity and precision of cavity enhanced spectroscopies, as well as other laser and synchrotron methods. Using cavity ringdown spectroscopy as well as synchrotron-based mass spectrometry, we have examd. the gas phase reactions and fundamental spectroscopy of free radicals crit. in the formation of photochem. smog. Frequency-stabilized cavity ringdown spectroscopy, developed at NIST by Hodges and co-workers, have provided us with the precision to measure spectroscopic parameters of greenhouse gases needed for remote sensing by the new generation of missions such as NASA's Orbitting Carbon Observatory, OCO-2, as well as the sensitivity to detect fugitive hydrocarbon emissions in situ. Finally, I present expts. demonstrating the potential of recently developed frequency comb lasers for high sensitivity, broad band detection of free radicals and transient intemediates in gas kinetics expts.