Spin–orbit splitting in the ground X2 Π electronic state of the and molecular ions

Abstract

Potential energy curves for electronic states 2Π1/2 and 2Π3/2 of the and molecular ions have been calculated in the framework of the spin–orbit multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT) under model core potential (MCP) methods. In the present theoretical study, the calculated potential energy curves were fitted to analytical potential energy functions (APEF) using the Murrell–Sorbie potential function, from the which accurate spectroscopic parameters were derived. The spin–orbit coupling constants for and were determined to be 463.990 and 545.734 cm−1, respectively, at the MCQDPT/MCP level, which are in good agreement with the experimental values. In addition, the theoretical spin–orbit coupling constants for S (3P2,1,0) were also found to be consistent with the experimental results.