In this project in the Theoretical and Computational Chemistry Program of the Division of Chemistry, investigations are being carried out to elucidate the mechanisms of photodissociation, geminate recombination, and vibrational relaxation of diatomic negative ions imbedded within molecular clusters. These ions include diatomic halogen anions solvated by carbon dioxide molecules. The methods of electron transfer theory are being combined with molecular dynamics simulations to study the interplay between charge localization and solvation. %%% Molecular ions in the gas-phase can become "solvated" by surrounding neutral molecules in much the same way as metal ions become "solvated" by water molecules in aqueous solution. In this study theoretical and computational methods are being used to characterize such clusters and their interactions with light.