Dipole excitation of Na clusters with a non-local energy density functional

The elementary dipole excitations of the ionized clusters Na ₉ ⁺ , Na ₂₁ ⁺ and Na ₄₁ ⁺ are investigated by solving the equations of the Random-Phase Approximation. The ground and excited states are described using the jellium model for the ionic background and a non-local energy density functional for the valence electrons. Non-local effects are specifically analyzed. The excitation energies thus obtained approach better than those of the Local Density Approximation both the full Hartree-Fock and the experimental results.