Fully relativistic computation on the electronic structure of I2 and I2+
Résumé
The study of non-adiabatic interactions in diatomic molecules provides solu- tions to fundamental problems of modern chemical physics and molecular spectroscopy such as van der Waals complexes formation and atomic collision. In this context, I2 and I2+ are interesting cases, since they have many valence molecular states corresponding to three dissociation limits: I(2P3/2) + I(2P3/2), I(2P3/2) + I(2P1/2) and I(2P1/2) + I(2P1/2), 18 ion-pair(IP) (I++I{) states and several Rydberg states within energy range below 10 eV. The potential energy curve (PECs) of these states are embedded each other. There shall be many perturbations between states in iodine molecule.
We carry out equation of motion-coupled cluster (EOM-CC) and multi-reference configuration interaction (MRCI) calculation respectively by relativistic ab initial quantum chemistry package Dirac. In order to sufficiently consider the relativistic effect of iodine, both two methods use default four-component Hamiltonian (Dirac-Coulomb). According to PECs, the spectroscopic constant of bound state is evaluated by LEVEL 8.0 program.
We show that the EOM-CC and MRCI describe well low-lying states in bound region, and with MRCI, we are able to describe the dissociation limits and reproduce total of 18 IP states of experiments.