Electronic States and Potential Energy Diagram of the Iodine Molecule

The existing spectroscopic data on the iodine molecule have been reanalyzed, some new assignments proposed, and a potential energy diagram computed for some ten electronic states up to 55 000 cm−1. In particular, the following new assignments have been made for the upper levels of certain absorption bands—(1) a repulsive Σu+3(0u−) to the weak absorption at λ2700 in iodine vapor, (2) an ionic Σu−3(0u+) to the PRKM and Skorko band systems, and (3) a state arising from the mixing of a homopolar Π0+3(0u+u) and an ionic Σu+1(0u+) to the Cordes bands. In addition, the λ3416 and λ4300 ``continua'' have each been interpreted satisfactorily as a region of unresolved, overlapping bands with a lower limiting frequency. Other states lying in the region 40 000–55 000 cm−1 have been established. New methods have been used to deduce segments of upper state potential energy curves.