Abstract: The electronic states of InI molecule are computed using the coupled-cluster single- and double-linear response theory (CCSD-LRT) based on the relativistic effective core potential basis sets. The spectroscopic constants of the 12 valence states and 4 bound Rydberg states, including the excitation energy (Te), the equilibrium bond distance (Re), and the vibrational constants (ωe and ωeχe), are obtained. Meanwhile, we obtain potential energy curves (PECs) of the electronic states. The results match well with the experimental data. There are some states with shallow potential wells at about 33 000 cm－1 above the 1Π state. The observed continuous absorption band system at about 31 500 cm－1 can be contributed to the transitions from these states and the 1Π state to the ground state.

Key words: InI, Coupled-cluster single- and double-linear response theory (CCSD-LRT), Relativistic effective core potential(RECP)