Near-field resonances in photon emission via interaction of electrons with coupled nanoparticles

In this work we construct the first-principles theory for the near-field resonances arising in the system of two different coupled nanoparticles excited by the external field. The obtained expressions are valid for an arbitrary external field; the detailed analysis is performed for the case of a fast electron passing by. The energy of electron is arbitrary, so the results are valid both for relativistic and nonrelativistic electrons. We have obtained rigorous analytical solution for the radiation field and for distribution of radiation over angles and frequencies. The effect of interaction between the single particles manifests itself very distinctly in conditions of resonance, resulting in a spectral shift of the radiation maximum, significant increase of its altitude, and, interestingly, in clear oscillations in radiation intensity not only when the particles are very close to each other, but even when the distance between the particles exceeds considerably their sizes. It attests to the strong influence of interaction on the radiation processes in a system of coupling particles.