Ab initio study on the low-lying potential energy curves of the diatomic cesium iodide cation (CsI)

Kurosaki, Yuzuru; Yokoyama, Keiichi  

Potential energy curves (PECs) for the low-lying states of the diatomic cesium iodide cation (CsI) have been calculated using the internally-contracted MRSDCI method with relativistic pseudpotentials. First, we calculate PECs for spin-orbit (SO)-free -S states, and , stemming from the triply degenerate P state of I. Then we obtain PECs for SO-included states, X3/2, 1/2(I), and 1/2(II), by diagonalizing the matrix of the electronic Hamiltonian plus SO coupling. It is found that all of the three state PECs, X3/2, 1/2(I), and 1/2(II), have shallow wells with the depths of 1.4-4.6 kcal mol. It is also predicted that transition dipole moments (TDMs) among these states have values of non-negligible amounts around equilibrium internuclear distances and the TDMs can contribute to the optical transition between the states.