AB INITIO POTENTIAL ENERGY SURFACES FOR THE $I(^{2}P_{3/2})+O_{2}(a^{1}\Delta_{g})\leftrightarrow I(^{2}P_{1/2}) + O_{2}(X^{3}\Sigma^{-}{_{g}})$ ENERGY TRANSFER PROCESS

Abstract

Ab initio electronic structure calculations have been used to investigate the electronic energy transfer process: $I(^{2}P_{3/2})+O_{2}(a^{1}\Delta_{g})\leftrightarrow I(^{2}P_{1/2})+O_{2}(X^{3}\Sigma^{-}{_{g}})$ Potential energy surfaces for all states associated with the reactants and products were obtained using CASSCF and CASPT2 methods, including the effective one-electron spin-orbit Hamiltonian. Surfaces correlating with the reactants and products were all found to be non-bonding. Shallow van der Waals minima were predicted at long range. Surface crossings were found at energies below the $I(^{2}P_{3/2})+O_{2}(a^{1}\Delta_{g})$ asymptote. It is probable that these crossings are responsible for the efficient transfer of electron energy in this system.