Fig. 2
From: Direct observation of polymer surface mobility via nanoparticle vibrations
The effect of particle interaction on the eigenmode spectrum. a Calculated phonon dispersion (Γ-X) of an fcc cluster made of cut spheres with diameter d = 141 nm and contact area of radius a0 = 14 nm, constituted by homogeneous polystyrene material (c1 = 2350 m s−1 and ct = 1210 m s−1). The Brillouin active branches deriving from the (s,1,1) and (s,1,2) of the single sphere are marked with red solid lines. The weakly and non-active branches deriving from (s,2,1) and the torsional modes, respectively, are indicated with green solid lines. The arrows on the right axis indicate the frequencies of the Brillouin active modes of the single particle. b Schematic diagram of Brillouin spectra for single particle (a0 = 0) and fcc cluster (a0 > 0), based on the dispersion in (a). The long and short blue arrows indicate the peak and the 20% pf the peak intensity positions
