Electric field inside a metal nanoparticle?

Question

In localized surface plasmon resonance, the conduction electrons of a metal nanoparticle oscillate in tune with the frequency of the incident electromagnetic wave . The effect is dominated by electrons present on the surface of the particle as it is a nanostructure and surface atoms constitute a major portion of total number of atoms.

As a dipole mode is created , electric field strength nearby the particle on outside is increased but what happens inside the volume of the nanoparticle ?

For a small metallic nanoparticle , let us say 20 nm , the field (considereing a 500nmEM wave)totally penetrates the particle and the electrons of the whole particle (volume + surface ) will resonate at plasma frequency, then there will be a field gradient generated inside the particle too but inside metals , a field cannot exist.

I am a little confused in this aspect.

Answer 1

It is an approximation to say that an electric field cannot exist inside a conductor.

Electrons can move freely inside a conductor. If a field exists, electrons will move. The nuclei do not move. so the result of electron motion is to reduce the field. This quickly drives the field to 0.

This breaks down at the surface. Electrons can move no farther. So a conductor in an electric field has a surface charge and no interior field.

But the electrons are not exactly at the surface. The charge density decays exponentially with depth.