Ground and excited states of the Ne +3 molecule

Abstract

Quantum-chemical ab initio calculations were performed for the electronic ground state and several low-lying excited states of the Ne 3 + molecular ion. Large parts of the potential energy surfaces, including the global minimum of the ground state, were treated by means of multi-reference many-body perturbation theory, starting from the SCF wave function of neutral Ne 3. For the inductive local minima of the ground state at C ∞v and C 2v geometries, the multi-configuration coupled electron-pair approach was used, together with an extended basis set. In agreement with the best previous calculations, we obtain a symmetric linear (D ∞h) equilibrium geometry for the Ne 3 + ground state, with a bond distance of 3.55 a.u. and a binding energy of 0.10 eV relative to Ne 2 + and Ne. In addition to this global minimum, two local minima exist, which correspond to a Ne 2 + ion in its electronic ground state ( R e=3.27 a .u.) binding a Ne atom by inductive forces. Both these minima are very shallow (0.07 and 0.03 eV for the C ∞v and C 2v structures). Potential energy surfaces for several low-lying excited states of Ne 3 + were calculated as well and their properties, e.g. adiabatic and vertical excitation energies, local minima, and dissociation channels, are discussed.