Plots of the linewidth, FWHM, versus the energy of the upper level of the transition, E_up. The species are grouped as in Fig. 5. All the detected species and the relevant isotopologues of Table 5 are plotted, except those in which the lines obviously have non-Gaussian profiles (see text). In particular, the labels HCN* and OCS* mean that the main isotopologues of these species are not included, because of their non-Gaussian profiles. The one-σ error bars include fit and spectral resolution uncertainties. The horizontal line at 5 km s^-1 corresponds approximatively to the average of the line FWHM range.