Emission cross sections and line shapes for photodissociating triiodide in ethanol: Experimental and computational studies

Resonance Raman spectra and emission cross sections have been measured for triiodide in ethanol. The spectra show a long progression in the symmetric stretch and a broad background, which we attribute to a combination of solvent-dephasing-induced fluorescence and unresolved Raman combination bands of the symmetric and antisymmetric stretches. We also observe the fundamental of the antisymmetric stretch, indicating that the symmetry of the triiodide ion is broken by the environment on the resonance Raman time scale. Using two skewed LEPS potentials to describe the excited states, we are able to calculate emission band shapes and cross sections that agree very well with experiment. However, the time scale for solvent-induced electronic dephasing is unclear due to the difficulty in partitioning the broad background into separate Raman and fluorescence contributions.