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 ${}^3{\Sigma }_u^{+}{\text{(0}}_u^{-})$ to the weak absorption at λ2700 in iodine vapor, (2) an ionic ${}^3{\Sigma }_u^{-}{\text{(0}}_u^{+})$ to the PRKM and Skorko band systems, and (3) a state arising from the mixing of a homopolar ${}^3{\Pi }_{0^{+}u}{\text{(0}}_u^{+})$ and an ionic ${}^1{\Sigma }_u^{+}{\text{(0}}_u^{+})$ 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.