15min:

VALERIO LATTANZI, M. C. MCCARTHY, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, and School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138; AND FILIPPO TAMASSIA, Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, V.le Risorgimento 4, I-40136 Bologna, Italy.

Molecules closely-related to SO₂ are of considerable interest because of the important role this triatomic or its surrogates play in the atmospheric and combustion chemistry of sulfur-containing compounds. Previous coupled-cluster quantum chemical calculations of the [HSO₂] potential energy surface conclude that a cis- isomer is the ground state, the trans isomer is a transition state, and that a C_2v HSO₂ isomer lies considerably higher in energy ( ~20~kcal/mol). Using Fourier Transform microwave spectroscopy, the rotational spectrum of the cis- HOSO radical has been precisely characterized for the first time by applying a DC discharge to a mixture of water and sulfur dioxide heavily diluted in neon. The fundamental rotational transition was detected near 17 GHz, in good agreement (within ~1%) of the calculated value derived from the equilibrium structure. Microwave-microwave double resonance techniques have been used to extend the dataset to higher frequencies and to provide confirmation of the spectroscopic assignments.