Spin–orbit coupling in I·CO2 and I·OCS van der Waals complexes: beyond the pseudo-diatomic approximation

We investigate theoretically the electronic structure of I·CO2 and I·OCS van der Waals complexes including spin–orbit interaction. For the T-shaped geometry of I·CO2, we calculate the potentials using a fully polyatomic treatment and compare the results to the widely used pseudo-diatomic approximation. The latter becomes increasingly invalid at I–CO2 distances shorter than 4 Å. We calculate the potentials of linear I·SCO and I·OCS, and analyze the zero-order electronic structure of nonlinear I·OCS. We also discuss the validity of treating the spin–orbit interaction in I·CO2 and I·OCS as an atomic property of iodine and find this approximation justified at characteristic van der Waals distances.