Potential energy curves for the collisional excitation of the (HeNe)+ system

The adiabatic spectrum of potential energy curves, corresponding to the 2Σ+ and 2Pi states of the molecular complex, have been calculated using an ab initio configuration-interaction method. Curve-crossing phenomena are found in all the curves with the exception of the lowest 2Σ+ state, corresponding to the Ne+(2P) + He(1S) asymptotic level. An approximate threshold of 22 eV is predicted for the neon 1S to 1P excitation, which is in good agreement with available experimental predictions. The charge-exchange excitation of Ne in the Ne+ + He collision occurs at about 29 eV in the 2Pi state for an internuclear separation of 1.5a0. Three additional crossings for the 2Pi spectrum are also found at lower energy and larger separation. The cross section for the first 2Σ+ crossing is calculated as a function of collision energy using the Landau-Zener-Stueckelberg method, and including the phase-interference effect. Phase-interference (''Stueckelberg'') oscillations are found in the cross section and are in qualitative agreement with oscillations found in the experimental cross sections