Electronic Structure and Electric Dipole Properties of the AgK Molecule: An Adiabatic and Diabatic Study

ABSTRACT An ab initio investigation of the AgK molecule is carried out within both the adiabatic and diabatic representations for low‐lying electronic states of ∑ + , Π and Δ symmetries below the ionic dissociation limit . Potential energy curves, spectroscopic constants, vibrational properties, and permanent and transition electric dipole moments were computed using a pseudopotential approach combined with full configuration interaction calculations. The calculated spectroscopic constants for the X 1 ∑ + , D 1 ∑ + , a 3 ∑ + and (2) 1 Π states show good agreement with the available theoretical and experimental data, supporting the reliability of the adopted methodology. The adiabatic potential energy curves exhibit numerous avoided crossings that govern the redistribution of ionic character and induce strong non‐adiabatic interactions between neighboring electronic states. To describe these interactions consistently, a diabatization procedure based on the variational effective Hamiltonian formalism was implemented, yielding diabatic potential energy curves and dipole moment functions. The resulting diabatic permanent dipole moment of the ionic state exhibits the expected linear dependence on the internuclear distance, providing a clear signature of its charge‐transfer character. These results provide useful theoretical data for future spectroscopic and quantum dynamical studies of cold and ultracold AgK molecules.