Ab initio and diatomics in molecule potentials for I2−, I2, I3−, and I3 (original) (raw)

The electronic structure of the I3− molecular anion and its photoproducts I2−, I2, and I3 were studied. Ab initio calculations were carried out using the multireference configuration interaction (MRCI) method for the valence electrons together with a relativistic effective core potential. The ab initio wave functions were also used to compute some spin–orbit coupling matrix elements, as well as approximate valence bond wave functions, used as guidelines in the construction of a 108-state diatomics in molecule (DIM) description of the electronic structure of I3−. In the DIM model, spin–orbit coupling was introduced as a sum of atomic operators. For I2− the ab initio and the DIM ground-state potentials show excellent agreement with the experimental results. The results for I2 are also in very good agreement with experimental data. For I3−, the MRCI calculations give a very good description of the spectroscopic constants and agree with the vertical excitation energies, provided spin–or...