Quantum scattering equations for non-adiabatic transitions in collisions between a Hund case (c) diatomic molecule and a structureless atom with application to I2(E0+g) + Ar

Time-independent quantum scattering close coupled equations are derived for non-adiabatic collisions involving a Hund case (c) diatomic molecule and a structureless particle. Infinite-order sudden and/or exponential distorted wave approximations are introduced to reduce the size of the system of close-coupled equations. The theory developed is applied to the study of non-adiabatic transitions between the first-tier ion-pair electronic states of an iodine molecule in collisions with Ar atoms. Calculations of cross sections and rate constants indicate the necessity of the close-coupling treatment of the vibronic channels and provide qualitative agreement with available experimental data