Quantitative study on the ground and low-lying electronic states of the KN+ cation

In this study, high-level ab initio calculations were performed for the diatomic cation KN⁺, a system not yet systematically explored experimentally or theoretically, by using the internally contracted multireference configuration interaction method with Davidson correction and the all-electron ANO-R basis set. We have explored its molecular structures, electronic properties, and transition characteristics in detail by focusing on twelve Λ-S states related to the five lowest dissociation channels. Potential energy curves, spectroscopic constants, and vibrational energy levels are determined for the cation. Regarding the ground state X⁴Σ^-, the equilibrium bond length, harmonic vibrational constant, and dissociation energy is calculated to 3.09Å, 97.6 cm^-1, and 0.09 eV, respectively. The effect of spin-orbit coupling on the electronic states is also examined and is proved to be insignificant. To better understand transition behavior of the cation, we have obtained key spectroscopic parameters, including transition dipole moments from excited Ω states to the ground state, Einstein A coefficients, Franck–Condon factors, and radiative lifetimes. The presented results offer useful reference data to guide future experimental and theoretical investigations of KN⁺.