Photoabsorption of sulfur dioxide cluster anions

Photodissociation and photodetachment of negatively charged sulfur dioxide clusters (SO₂) _n ^? ,n=2–11, were investigated in the wavelength range from 458 to 660 nm. Electrons obtained from the interaction of photons with clusters were found to be produced in two photon processes forn≥3. Hence their detachment threshold energy is increased by at least 0.7 eV with respect to the dimer. Wavelength dependent depletion spectra indicate that the clusters are composed of a dimer anion chromophore solvated by neutral molecules. The spectral position of the absorption band is maintained and the shape evolves continuously with cluster size. However, a narrowing of the band with increasing cluster size is observed.