Charge density in metal nanoparticles at plasmon resonance

It is important to know the magnitude and distribution of electric field near the metallic nanoparticles at plasmon resonance. One can look at the electric field and say whether the plasmon mode is dipolar or higher order mode such as qudrapolar mode. At many times one is also interested to know the surface charge density which makes easier to identify the plasmon mode. One can get the surface charge density by talking the divergence of electric field (near field) either calculated by DDA method or FDTD method [Reference paper]. Below I have calculated the electric field near nanoparticle at plasmon resonance using FDTD method and also calculated the corresponding surface charge density. One can see the dipolar nature of the electric field, and also the surface charge density maximum at one end of the particle and minimum at the other end. Surface Charge density plots become more useful when analyzing complex geometries with complex modes.

[caption id="attachment_655" align="alignnone" width="300" caption="Electric field and charge density distribution"][/caption]