Time-dependent density-functional calculations for optical spectra of Na-2 and Na-4 clusters

With the frame of the time-dependent local density approximation, an efficient description of the optical response of clusters has been used to study the photo-absorption cross section of Na-2 and Na-4 clusters. It is shown that our calculated results are in good agreement with the experiment. In addition, our calculated spectrum for the Na-4 cluster is in better agreement with experiment than the GW absorption spectrum.