ii (ω) without renormalization by their intensities, in order to better visualize the bands and the corresponding absorption regions. The reported power spectra were smoothened out by performing a locally estimated scatterplot smoothing (LOESS), to attenuate the significant noise of the bare spectra. The bare spectra were all normalized to unity when integrated over the whole spectral domain before applying the LOESS procedure. Differences in intensities when the bands have different delocalizations are then justified by the normalization. All along the analysis and bands assignment procedure, the modes were labelled with their average frequencies, which are defined as the average values over the bare normalized spectra.