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Download fileNumerical Calculations of Radiative and Non-Radiative Relaxation of Molecules Near Metal Particles
journal contribution
posted on 22.05.2014, 00:00 authored by Maxim Sukharev, Noa Freifeld, Abraham NitzanThe
dependence of the radiative emission and the nonradiative (energy
transfer to the metal) relaxation rates of a molecule near a small
metal particle on the molecule-to-particle distance and on the molecular
orientation is calculated using a numerical solution of the Maxwell
equations for a model that described the metal as a dispersive dielectric
particle and the molecule as an oscillating point dipole. The emission
rate is obtained by evaluating the total oscillating dipole in the
system, while the nonradiative rate is inferred from the rate of heat
production on the particle. For the distance dependence of the nonradiative
rate we find, in agreement with experimental observations, marked
deviation from the prediction of the standard theory of fluorescence
resonance energy transfer (FRET). In departure from previous interpretations,
we find that electromagnetic retardation is the main source of this
deviation at large molecule–particle separations. The radiative
emission rate reflects the total dipole induced in the molecule–particle
system, and its behavior as a function of distance and orientation
stems mostly from the magnitude of the oscillating polarization on
the metal particle (which, at resonance, is strongly affected by plasmon
excitation), and from the way this polarization combines with the
molecular dipole to form the total system dipole.