Abstract: Plasmon excitation in small sodium clusters with triangle structure is studied with time-dependent density functional theory. For relatively larger sodium clusters,along triangle bottom edge and perpendicular bisector of triangle bottom edge,linear shapes of absorption spectra and resonance energies of main absorption peaks are same. However,along these directions,resonance modes of main absorption peaks are different. For the main plasmon mode,field enhancement extrema are located in region of endpoints of the triangle.

Key words: plasmon excitation, time-dependent density functional theory, clusters