Relativistic and correlated calculations on the ground, excited, and ionized states of iodine

The electronic structure, spectroscopic, and bonding properties of the ground, excited, and ionized states of iodine are studied within a four-component relativistic framework using the MOLFDIR program package. The experimentally determined properties of the Σg+1 ground state are well reproduced by our results calculated at the CCSD(T) level of theory. Relativistic effects and core–valence correlation need to be included in order to get reliable results, but the Gaunt interaction can be neglected. The photoelectron spectrum and the potential energy curves of the ionized and excited states are calculated using relativistic configuration interaction and coupled cluster methods. The calculated properties of the excited states are generally in good agreement with the experimental data, as well as with the earlier theoretical results of Teichteil and Pelissier. An alternative assignment of some recently measured, low lying, ionized states is proposed.