Potential Energy Curves and Lifetimes of Low-Lying Excited Electronic States of CSe Studied by Configuration Interaction Method

In this work, we performed a high level ab initio study on the low-lying electronic states of CSe, utilizing MRCI+Q (the internally contracted multireference configuration interaction, and Davidson’s correction) method with scalar relativistic and spin–orbit coupling effects taken into account. The potential energy curves of 18 Λ–S states associated with the lowest dissociation limit of CSe molecule, as well as those of 50 Ω states generated from the Λ–S states were computed. The spectroscopic parameters of bound states were evaluated, which agree well with existing theoretical and experimental results. With the aid of calculated spin–orbit matrix elements and the Λ–S compositional variation of the Ω states, the spin–orbit perturbations of low-lying states to the A1Π and a3Π states are analyzed. Finally, the transition dipole moments of A1Π, A′1Σ+, a3Π0+, and a3Π1 to the ground X1Σ+ state as well as the lifetimes of the four excited states were evaluated.