Abstract
In a broad size range, we examine how dipolar surface plasmons in spherical small particles are composed of their constituent electronic transition processes. A series of transition processes satisfying specific selection rules are found to play the leading part in formation of the surface-plasmon mode. As the number of these leading transition processes becomes larger with increase in size, the mode assumes more collective-excitation character, and evolves into a more complete surface excitation having its induced charges more sharply localized around the surface. Our decomposing analysis shows how the above transition processes create a surface excitation and yield the giant resonance in a photoabsorption spectrum.
