Ab initioabsorption spectra ofAln (n=2–13)clusters

Abstract

We investigate the optical absorption spectra of ${\mathrm{Al}}_{n}$ $(n=2--13)$ clusters using the time-dependent spin-polarized local-density approximation. The overall shapes of the calculated spectra strongly depend on cluster geometries. It is observed that a simple jellium model is not valid for these clusters. In the size range of $nl~5,$ the spectra show discrete, atomiclike transitions. For $n=6--12,$ the shape of the absorption spectra can be explained on the basis of an ellipsoidal shell model. A strong collective excitation peak is observed for ${\mathrm{Al}}_{13}$ cluster, which is due to its spherical symmetry.