Potential energy curves for the ground and low-lying excited states of IBr calculated with relativistic effective core potentials and spin–orbit interactions

Low-lying potential energy curves of the IBr molecule are calculated by a combination of the equation of motion coupled cluster method and the spin–orbit multireference configuration interaction with single excitations, employing in both cases accurate relativistic effective core potentials and an extended valence basis set. Dissociation curves and spectroscopic constants are presented for the ground and eight lowest excited states and the relation of the results to experiment is discussed.