Excited-State Reaction Dynamics of Chlorine Dioxide in Water from Absolute Resonance Raman Intensities

Abstract

Resonance Raman spectra of aqueous chlorine dioxide (OClO) are measured for several excitation wavelengths spanning the photochemically relevant 2B1−2A2 optical transition. A mode-specific description of the optically prepared, 2A2 potential energy surface is derived by simultaneous analysis of the absolute resonance Raman and absorption cross sections. The resonance Raman spectra are dominated by transitions involving the symmetric stretch and bend coordinates demonstrating that excited-state structural evolution occurs predominately along these degrees of freedom. Scattering intensity is not observed for transitions involving the asymmetric stretch, demonstrating that excited-state structural evolution along this coordinate is modest. The limited evolution along the asymmetric stretch coordinate results in the preservation of C2v symmetry on the 2A2 surface. It is proposed that this preservation of symmetry is responsible for the increase in Cl photoproduct quantum yield in solution relative to the gas ...