The focus of this dissertation is to decipher the previously unknown reaction dynamics of NO3 photodissociation. Although the NO + O2 products are known to catalyze atmospheric ozone destruction, the mechanism by which these products are formed has remained a mystery, and no energetically accessible transition state has ever been calculated. Using velocity map ion imaging experiments to carefully study the stereochemistry of the product fragments combined with theoretical calculations performed by Drs. Xiao, Maeda, and Morokuma at Kyoto University, we have determined that the reaction proceeds exclusively via the unusual "roaming mechanism," with no evidence of a competing traditional transition state pathway. Within, the significance of this discovery is discussed in regards to both the NO3 system and roaming dynamics in general, for which this system has provided new insight.