The Crystal Field Plasmon Splitting

We present an electromagnetic analogue of crystal (or ligand) field theory that describes geometric eigenmodes and the resonant plasmon wavelength in plasmonic nanocrystals in terms of a simple shape descriptor. Our model, crystal field plasmon splitting, is based on secular equations for geometric eigenmodes, allowing for the separation of pure shape from materials effects. As an example, the model is implemented to the experimental gold nanoparticles that undergo cube-to-sphere transition, showing that geometric eigenvalues change correspondingly in analogy to the atomic energy levels in Tanabe-Sugano correlation diagrams.