Figure 1: Calculated SERS EFs for Au nanoparticle chains using generalized Mie theory. The EF spectra have been calculated for chains ranging 1–9 nanoparticles in length with excitation source parallel to the long axis of the chain for an interparticle gap of 1 nm and 𝑛 e = 1 . 0 (a) and an interparticle gap of 1.5 nm and 𝑛 e = 1 . 5 (b). The EF for the 632.8 nm excitation source for (a) and (b) are shown, respectively, in (c) and (d). Angular momentum contributions up to the 37th order were included in the GMT calculations. The integral was taken at a distance of 0.5 nm from the particle surface for (a) and 0.75 nm from the particle surface for (b). The two enhancement peaks for the 𝑁 = 5 chain are identified as II and I, respectively, in (b).