Simulating Plasmon Resonance

Hello,

I am trying to simulate plasmon resonance on the surface of a spherical gold nanoparticle with a 40nm radius, and I've been running into difficulties. According to our Mie theory calculations, the extinction cross section spectrum should look like this:



However, the best result I've been able to get looks like this



As you can see, the shape of the graph is mostly there, but the short wavelengths and magnitudes of the extinction cross section are off. I have attached the code that I have been using. I am a formulation given in
on page 43 of this paper:

www.research-collection.ethz.ch/bitstrea...quence=2&isAllowed=y

and am calculating the extinction cross section extinction using equation 35 of this paper:

people.atmos.ucla.edu/liou/Group_Papers/Yang_JOSAA_13_1996.pdf .

I have attached the code that I have been using. Is this discrepancy between NGSolve and Mie theory the result of not having enough degrees of freedom, or am I using NGSolve incorrectly?



Any help would be greatly appreciated