Spectroscopy of atmospherically relevant inorganic acids.

摘要

This thesis presents a study of O-H stretching vibrational overtones of atmospheric chromophores. Experimental spectroscopic results are presented for gas-phase nitric acid and sulfuric acid complemented by electronic structure calculations. Much of my analysis focuses on the O-H stretching vibrations in these acids. The results are discussed in the context of atmospheric chemistry to better understand the physical and photochemical properties of HNO3 and H2SO4.;I obtained a gas-phase spectrum of HNO3 in the near-infrared (2000--8500 cm-1) and assigned the vibrational transitions, including overtones and combination bands. These spectroscopic frequencies and intensities are discussed for the observed transitions. I also compare my experimental results to several recent theoretical methods that have predicted the potential energy surface of HNO3 as well as its vibrational frequencies and intensities.;In Chapter 4, I discuss the highest-resolution infrared spectroscopy of H2SO4 to date (0.05 cm-1), which also includes its isotopomers (HDSO4 and D2SO4). I use spectroscopic techniques to assign combination bands in the mid-infrared and near infrared and use ab initio theory to help explain spectral features and propose the existence of several stable rotational isomers of sulfuric acid.;Finally, I extend the spectroscopy of H2SO4 to the visible region, where I was able to observe its third and fourth O-H stretching overtones using cavity ring-down spectroscopy. I obtain the vibrational cross-sections for these transitions and use them to provide modified estimates of atmospheric J-values for the overtone-induced photodissociation of sulfuric acid. In addition, I compare trends in the O-H overtone frequencies and intensities of nitric and sulfuric acids and discuss the implications for their physical properties.