A CONFIGURATION-INTERACTION STUDY OF THE GROUND AND 1ST EXCITED 1-SIGMA+ STATES OF THE NAI MOLECULE

Multireference singly and doubly excited CI (MRSDCI) calculations are performed on the NaI molecule by using a model potential method. The potential energy curves of the ground and first excited 1-SIGMA+ states are generated over a wide range of internuclear distance R. The curves yield the avoided crossing, which is expected to arise by the mixing of the ionic and covalent configurations, and thus the curve of the first excited state shows a shallow minimum. The geometrical parameters, dipole moment, and dissociation energy are calculated. The agreement of those with the experimental results is satisfactory.