Top panel: normalized opacity of the (Al₂O₃)_n clusters convoluted with a Lorentzian profile with a FWHM of 0.03 μm. The full coloured lines represent the opacities normalized for each cluster entity separately (with the same colour coding as in Fig. 13), while the dotted coloured lines indicate the wavelength position of all ground-state vibrational frequencies of the stable (Al₂O₃)_n (n = 1−4) clusters. Middle panel: comparison between the (stellar continuum subtracted and normalized) SED of R Dor (full black line) and W Hya (full gray line) with the predicted vibrational frequencies of the stable (Al₂O₃)_n (n = 1−4) clusters (vertical coloured lines). The gray areas indicate the region with some of the largest (Al₂O₃)_n opacities. The dashed gray lines indicate the CO₂ lines as discussed by Justtanont et al. (2004). The full red line represents the (stellar continuum subtracted and normalized) emission for a slab model containing H₂O, SiO, and SiS. The column densities for all species were taken to be 1 × 10²⁰ cm^-2 at 0.5R_⋆ above the stellar surface for a temperature of 2000 K. The individual contributions of H₂O, SiO, and SiS are shown in the bottom panel. The column densities of the molecules were not chosen to fit the ISO/SWS data, but serve as illustrative examples on the molecular line veiling.