Theoretical electronic structure of the aluminium monoiodide molecule

Accurate theoretical spectroscopic constants and potential energy curves are obtained for the ground state ${\rm X}$1$\Sigma^{+}$ and the low-lying electronic states ${\rm A}$1$\Pi$, a$^3\Pi$ and b$^3\Sigma^{+}$of AlI molecule. The calculated values of Te, $\omega$e and re of the first three states are compatible with the experimental results. An ordering of states is represented for the lowest predicted singlet and triplet states. These results provide a big support to determine the analogy in the ordering of electronic states in AlF, AlCl, AlBr and AlI respectively at lower energies. These theoretical results characterize a set of electronic singlet and triplet states and identify for the first time the unobserved electronic state b$^3\Sigma^{+}$