Spectroscopic Reassignment and Ground-State Dissociation Energy of Molecular Iodine

Reanalyzing some early bandhead data for ${\mathrm{I}}_2{\text{[B 0}}_u^{+}{(}^3\mathrm{\Pi )]}$ , an improved value of the ground‐state dissociation energy is found to be $D_0\text{\hspace{0.17em}=\hspace{0.17em}12 440.9\hspace{0.17em}±\hspace{0.17em}1.1}{\mathrm{cm}}^{\text{−1}}$ , differing significantly from the previously accepted value of Verma, 12 452.5 ± 1.5 cm⁻¹. This result implies that the final state of one of the uv resonance series reported by Verma must have a rotationless potential maximum some 13.1 ± 1.4 cm⁻¹ high. It is further shown that the original electronic assignment of this state as ground‐state ${\text{X 0}}_g^{+}{(}^1\mathrm{\Sigma )}$ is implausible. A reassignment as $0_g^{+}{(}^3\mathrm{\Pi )}$ is proposed, and the nature of the $0_g^{+}{(}^3\mathrm{\Pi )}$ potential is considered.