Systematic Study of the Electronic Properties and Trends in the LiX (X = Na, K, Rb, Cs and Fr) Molecules

Alkali mixed diatomic molecules exhibit significant permanent dipole moment. They constitute a prototype of an ultra-cold quantum gas, which makes them candidates for fundamental quantum processes. This requires knowledge of their accurate electronic properties to guide the ongoing experiments. For this purpose, we have investigated the structure and spectroscopic properties of the first electronic states of (1,3)Sigma(+), (1,3)Pi, (1,3)Delta symmetries for LiNa, LiK, LiRb, and LiCs molecules. We have used an tab initio approach based on pseudopotential techniques: parameterized I-dependent polarization potentials and full configuration interaction calculations through the CIPCI quantum chemistry package. The spectroscopic constants (R-e, D-e, omega(e), omega X-e(e), and B-e) of these states are derived and compared with the available theoretical and experimental work. In addition to the potential energy, accurate permanent and transition dipole moments are determined for a wide range of internuclear distances. A systematic study and analysis of the trend of the permanent dipole moments around the equilibrium distance of the ground state of LiX (X =Na, K, Rb, Cs and Fr) molecules are done. The results, compared to available theoretical and experimental work, show good agreement.