Theoretical investigation of the alkali-dimer cation K 2 + : Potential energy,dipole moment and atomic polarizabilities

Abstract

The potential energy curves of the electronic states of ${}^2{\mathrm{\Sigma }}_{\mathit{g}\mathrm{,}\mathit{u}}^{+}$ , ${}^2{\mathrm{\Pi }}_{\mathit{g}\mathrm{,}\mathit{u}}$ and ${}^2{\mathrm{\Delta }}_{\mathit{g}\mathrm{,}\mathit{u}}$ symmetries of the ${\mathrm{K}}_2^{+}$ molecular ionic system dissociating into K (4s, 4p, 5s, 3d, 5p, 4d and 6s) + K⁺, have been calculated. The computation was performed using an ab initio approach, where a non-empirical pseudopotential for the K⁺ core has been involved and a core-core and core valence correlation corrections have been added. The spectroscopic constants have been derived and compared with the available theoretical and experimental works. A good agreement has been obtained for the ground and the first excited states. However, a clear disagreement between this study and the model potential work of Magnier and Aubert-Frécon [J. Quant. Spect. Rad. Trans. 78, 2003] has been observed for several excited states. They found that the $5^2{\mathrm{\Sigma }}_{\mathit{u}}^{+}$ , $6^2{\mathrm{\Sigma }}_{\mathit{g}}^{+}$ , $6^2{\mathrm{\Sigma }}_{\mathit{u}}^{+}$ , $7^2{\mathrm{\Sigma }}_{\mathit{g}}^{+}$ , $7^2{\mathrm{\Sigma }}_{\mathit{u}}^{+}$ , $4^2{\mathrm{\Pi }}_{\mathit{g}}$ and $2^2{\mathrm{\Delta }}_{\mathit{u}}$ states are repulsive, although they are attractive with potential well depths of 10, 100 and 1000 cm⁻¹ in our study. Furthermore, the atomic polarizabilities have been predicted from a vibrational spacing analysis based on the WKB approximation applied on the potential energy at long-range distances. These polarizabilities have been used to reproduce the long range potential interaction for some electronic states.