15min:

ENGELENE T. H. CHRYSOSTOM, TONY MASIELLO, JEFFREY BARBER, NICOLAE VULPANOVICI, JOSEPH W. NIBLER, Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331-4003; ALFONS WEBER, National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230; ARTHUR MAKI, 15012 24 th Ave. S. E. Mill Creek, WA 98012; THOMAS A. BLAKE, ROBERT L. SAMS, Pacific Northwest National Laboratory, P. O. Box 999, Mail Stop K8-88, 3020 Q Avenue, Richland, WA 99352.

Sulfur trioxide is an important participant in reactions in the upper atmosphere and also in a number of industrial processes. It is a D_3h planar oblate top whose spectroscopy is incomplete, perhaps in part due to its corrosive properties. We are engaged in a comprehensive investigation of the fundamental and combination-overtone bands of ³²S¹⁶O₃ as well as of the ³⁴S¹⁶O₃, ³²S¹⁸O₃ and ³⁴S¹⁸O₃ isotopic forms. High resolution (0.001 cm^-1) coherent anti-Stokes Raman scattering (CARS) was used at Oregon State University to determine for the first time the Q-branch structure of the IR-inactive ₁ symmetric stretching mode of ³²S¹⁶O₃ and its various isotopomers. The ₁ spectrum of ³²S¹⁶O₃ reveals two intense Q-branch regions, with surprisingly complex vibrational-rotational structure. The modeling of this has involved a subtle combination of Fermi resonance and indirect Coriolis interactions with nearby hidden states; 2 ₄ (\ell=0,\pm 2), ₂ + ₄ (\ell = \pm 1), 2 ₂ (\ell=0). The analysis of the perturbed ₁ spectrum was made possible by locating some of these states via concurrent infrared hot-band studies at PNNL by T.A. Blake et al. The results of this combined effort will be presented for ₁ of ³²S¹⁶O₃.