A first principles study of the spin-orbit coupling effect in LiM (M = Na, K, Rb, Cs) molecules

Area of Science:

• Quantum Chemistry
• Molecular Physics
• Spectroscopy

Background:

• Spin-orbit (SO) interactions are crucial for understanding electronic states in molecules.
• Accurate calculations of SO coupling are essential for predicting molecular properties and spectra.

Purpose of the Study:

• To investigate spin-orbit (SO) interactions in low-lying electronic states of the LiM (M = Na, K, Rb, Cs) molecular series.
• To compute potential energy curves and SO coupling matrix elements as functions of interatomic distance (R).

Main Methods:

• Ab initio calculations employing Fock-space relativistic coupled-cluster (FS-RCC) methods for direct relativistic energies.
• Configuration interaction with core-valence correlation via core polarization potentials (CI-CPP) for scalar-relativistic energies and SO coupling functions.
• Projection of scalar-relativistic wave functions onto full-relativistic counterparts to extract SO coupling functions.

Main Results:

• Calculated SO-free potentials and SO coupling functions show good agreement between the FS-RCC and CI-CPP methods.
• The results are consistent with prior theoretical and empirical data for the LiM molecular series.
• Accurate potential energy curves and SO coupling matrix elements were obtained.

Conclusions:

• Both employed computational approaches provide reliable data for spin-orbit interactions in LiM molecules.
• The study validates the accuracy of the ab initio methods for characterizing electronic states and SO effects.
• This work contributes to a deeper understanding of relativistic effects in alkali metal diatomic molecules.