Extinction characteristics of a gold nanorod in water ( n = 1.33). (a) The configuration of the numerical modeling. (b) Simulated extinction spectra of the gold nanorod for different incident angles θ; the extinction value in the left panel is normalized to the quadrupole peak for θ = 45°, and in the right panel to the dipole peak for θ = 0° (with a scale 3.36 times larger than the left panel). Curves are plotted with offset for clarity. (c) Angle-dependent peak extinction for the dipole, quadrupole, and sextupole resonance modes, normalized to the maximum values of each mode.