A probe of dynamical models using functional sensitivity densities with application to He⁺+Ne(2 p⁶)→He⁺+Ne(2 p⁵3 s) and Li+I→Li⁺+I^-

The functional sensitivity densities δ ln σ₁₂(E)/δ ln V_ii(R) for He⁺+Ne(2 p⁶)→He⁺+Ne(2 p⁵3 s) reveal that the collisional excitation cross section σ₁₂(E) is insensitive to the additional diabatic curve V₃₃ included in some models. The negligible sensitivity of σ₁₂(E) to V₃₃ offers a quantitative validation of the more popular two state model for collisional excitation of Ne by He⁺. The sensitivity profiles for the collisional ionization Li+I→Li⁺+I^- modeled by crossing diabatic curves V₁₁ (covalent) and V₂₂ (ionic) shows that the ionization cross section does not depend on inner crossings even when these stem from large distortions in the underlying potential energy curves. The lack of sensitivity to inner crossings establishes the predominant role of the outermost crossing in triggering nonadiabatic transitions.