Multireference configuration interaction study on the potential energy curves and radiative lifetimes of low-lying excited states of CdH⁺ cation

Highlights: • The excited states of CdH⁺ have been studied by multi-configuration wavefunctions. • The SOC effect on CdH⁺ is accounted for via state interaction method. • Our spectroscopic results support the early experimental data. • The PDMs and SO matrix elements reveal the abrupt changes at R_ACP. • The abrupt changes are explained with the aid of the wavefunctions. - Abstract: Ab initio calculations on CdH⁺ cation have been performed with the high-level relativistic MRCI + Q method. The potential energy curves of seven low-lying Λ–S states, correlated with the dissociation limits Cd⁺(²S_g) + H(²S_g), Cd(¹S_g) + H⁺(¹S_g), and Cd⁺(²P_u) + H(²S_g), are computed. And the accurate spectroscopic constants of the bound Λ–S are determined. The permanent dipole moments (PDMs) of Λ–S states as well as the spin–orbit matrix elements are evaluated. The results indicate that the abrupt changes of PDMs and the spin–orbit matrix elements are attributed to the change of the electronic configurations at the avoided crossing point. After considering the spin–orbit coupling (SOC) effect, the 12 Ω states generated from the Λ–S states are investigated. It is indicated that the SOC effect is substantial for CdH⁺, leading to the double-well potential of (3)0⁺ state. Finally, the transition properties of several transitions are reported, including the transition dipole moments, Franck–Condon factors, and radiative lifetimes