Photodissociation dynamics of CH3I adsorbed on MgO(100): Theory and experiment

TLDR: Theoretical and experimental results for the 257 nm photolysis of methyl iodide adsorbed on an MgO(100) crystal were compared in this article, where the I*/I branching ratio and the velocity and angular distributions of both photofragments were predicted by the theory.

Abstract: Theoretical and experimental results are compared for the 257 nm photolysis of methyl iodide adsorbed on an MgO(100) crystal. Molecular‐dynamics calculations treat CH3I as a pseudodiatomic molecule and describe the geometry and the vibrational and librational frequencies of ground state CH3I on the surface of a solid at 125 K. The simulations modeled the photodissociation dynamics of the adsorbed species. The photoexcitation of CH3I at 257 nm is to the 3Q0 state which is, in turn, coupled to the 1Q1 state. The electronic surface coupling allows for two dissociation pathways, producing either ground‐ or excited‐state iodine atoms in concert with ground‐state methyl radicals. The I*/I branching ratio and the velocity and angular distributions of both photofragments are predicted by the theory. A comparison is made between these predictions and experimental observation of the I*/I branching ratio, the velocity distribution of the methyl fragment, and the internal state distribution of the methyl. A substanti...