Theoretical study of the electronic structure of mono-chloride of lanthanum molecule including spin-orbit coupling effect.

Our investigation is devoted to the theoretical study of the low-lying electronic structure of the LaCl molecule by using ab initio quantum methods. We are concerned with several methods such as the complete active space-self consistent field (CAS-SCF) and the multi reference of configuration interaction (MRCI + Q) methods. These methods are applied for the purpose of drawing the potential energy curves (PECs) and calculating the molecular spectroscopic constants for a given number of electronic states of singlet and triplet multiplicity. We count 26 2S+ 1 Λ(±) electronic states located below 24,000 cm- 1 neglecting the spin-orbit effects and 47 Ω(±) components taken into consideration these effects. Our calculations are performed via the quantum ab initio package MOLPRO (Werner and Knowles 2000). Graphical Abstract A new set of low-lying electronic states on the theoretical energetic level diagram for the LaCl molecule among the first four lanthanum monhalides.