CARS AND INFRARED STUDIES OF THE $\nu_{1}, \nu_{2}$ AND $\nu_{4}$ BANDS OF $^{34}S^{18}O_{3}$

Author Institution: Department of Chemistry, Oregon State University; National Science Foundation, National Institute of Standards and Technology; National Science Foundation, Pacific Northwest National LaboratoryWe are engaged in a comprehensive investigation of the spectroscopic properties of sulfur trioxide, an important participant in reactions in the upper atmosphere. The fundamental modes and several hot bands of the isotopic variants ($^{32}S^{18}O_{3}, {^{34}}S^{16}O_{3}$, and $^{34}S^{18}O_{3}$) have been investigated using high resolution infrared spectroscopy and coherent anti-Stokes Raman scattering. For all isotopic variants, the Raman-active symmetric stretching mode $\nu_{1}$ shows complex Q-branch patterns due to indirect Coriolis couplings, l-resonances, and Fermi resonances with dark $\nu_{2}, \nu_{4}$ combination/overtone levels. Essential to modeling the interactions of these levels with $\nu_{1}$ is the understanding of the fundamental vibrations that make up these levels. The analysis of the $\nu_{2}, \nu_{4}$ infrared active fundamental vibrations of $^{34}S^{18}O_{3}$ will be presented, along with efforts to model the complex $\nu_{1}$ CARS spectrum using information derived from studies of hot bands involving $\nu_{2}$ and $\nu_{4}$