Ionic structure and plasmon response in sodium clusters

The linear and nonlinear optical response of sodium clusters is studied using fully three-dimensional electronic dynamics with frozen ionic positions. The detailed ionic structure produces more spectral fragmentation than a comparable jellium model, and the fragmentation patterns come close to measured spectra, even at low temperatures. The nonlinear response shows the same trends as found in former, symmetry restricted, investigations, namely that the plasmon resonance is a very harmonic mode showing no trace of nonlinear effects as secondary harmonics or spectral diffusion.