Quantum Mechanical Examination of Optical Absorption Spectra of Silver Nanorod Dimers

Abstract

Time-dependent density functional theory calculations are employed to examine the optical absorption spectra of dimers of the pentagonal silver nanorods Ag₁₉ ⁺¹, Ag₂₅ ⁺¹, and Ag₃₁ ⁺¹. The qualitative features of the spectra agree well with the exciton-coupling model and with previous experimental and theoretical results. In the end-to-end orientation, longitudinal peak red-shifts with decreasing distance. For side-by-side dimers, the transverse peak splits as the interparticle distance decreases due to symmetry-breaking, and the longitudinal peak blue-shifts slightly with decreasing distance. Quantum mechanical calculations are required for the calculation of absorption spectra at very short interparticle distances where the electron densities of the two subsystems overlap. At short distances, the energies and intensities of the monomer peaks change substantially and new excitation peaks emerge