Particle Plasmons as Dipole Antennas: State Representation of Relative Observables

The strong interactions between light and plasmons (in metal nanoparticles) allow to observe chemical and physical processes on and around the particle on nanometer length scales as well as they allow to use plasmons for various applications. While electrodynamic theory predicts such effects very accurately, it is too complex to intuitively connect the underlying processes with the observed changes. The much simpler description of particle plasmons as harmonically driven dipole antennas has already been successfully used to describe many plasmonic effects. Here, these insights are combined and complemented to form a coherent and simple description of particle plasmons as dipole antennas. Unlike electrodynamic theory, this description connects fundamental plasmon properties such as shape, charges, environment, or surface coverage with spectroscopic properties like line width or resonance position. Therefore, this connection uniquely allows to identify the chemistry and physics behind the plasmonic responses and to intuitively predict the effects of various processes. The intuitive understanding is important to estimate the effects of complex processes, which occur in applications employing plasmonic nanostructures. To demonstrate the utility of this description, we untangled physical and chemical processes of changes in the plasmon observables during alkanethiol adsorption.