Geometry and Surface Plasmon energy

We derive a simple rule to determine surface plasmon energies, based on the geometrical properties of the surface of the metal. We apply this concept to obtain the surface plasmon energies in wedges, corners and conical tips. The results presented here provide simple and straightforward rules to design the energy of surface plasmons in severals situations of experimental interest such as in plasmon wave guiding and in tip-enhanced spectroscopies.