The potential energy curves and spectroscopic constants of the ground and several low-lying excited states of the Ca^q+-Kr (q = 0, 1, 2) van der Waals complexes were investigated using one- and two-electron pseudopotential approaches. This treatment effectively reduces the number of active electrons in Ca^q+-Kr to a single valence electron for q = 1 and two valence electrons for q = 0, allowing the use of large and flexible basis sets for both Ca and Kr atoms. Within this work, potential energy curves (PECs) were calculated at the SCF level for the Ca⁺-Kr system, while both SCF and full configuration interaction (FCI) calculations were performed for the neutral Ca-Kr. Spin–orbit coupling effects were explicitly included in all calculations to accurately describe the fine-structure splitting of the asymptotic atomic states. The short-range core–core interaction for Ca²⁺-Kr was obtained using high-level CCSD(T) calculations. Spectroscopic constants were derived from the computed PECs and compared with available theoretical and experimental results, showing consistent trends. Furthermore, the transition dipole moments (TDM) were evaluated as a function of internuclear distances, including spin–orbit effects, to provide a comprehensive description of the electronic structure and radiative properties of these weakly bound systems.

Adiabatic and diabatic potential energy curves of the LiS molecule from high-level ab initio calculations.

One and two electron pseudopotential approaches were employed to investigate the electronic and spectroscopic properties of the Mg ⁺ Xe and MgXe van der Waals complexes. In this study, potential energy curves (PECs) were computed at the SCF level for the Mg ⁺ Xe system, whereas both SCF and full configuration interaction (FCI) calculations were performed for the neutral MgXe complex. In addition, the core–core interaction, denoted as Mg ²⁺ Xe, was treated using the CCSD(T) method. Furthermore, spin–orbit coupling effects were explicitly included for the first excited B ² Σ ⁺ and A ² Π electronic states. Spectroscopic parameters obtained for the ground and low‐lying excited states are compared with existing experimental and theoretical results, showing good agreement and contributing to a deeper understanding of the interaction between Mg and Xe in various electronic states. The temperature dependence of the absorption spectrum of a Mg atom adsorbed on Xe _n ( n = 1–7) clusters is also investigated using a combined Monte Carlo (MC) method with basin hopping global optimization to simulate the geometries of the xenon clusters in the 3s–3p transition at temperature T. Transition dipole moments are also calculated for the X ² Σ ⁺ → A ² Π ₁ / ₂ , ₃ / ₂ and X ² Σ ⁺ → B ² Σ ⁺ ₁ / ₂ transitions.