1997A&A...325..269C

The relevance of dust in circumstellar emission has to be carefully considered in order to properly interpret astronomical observations. In this work we focus on carbon-rich planetary nebulae in order to produce models able to account for IR and submillimeter dust emission. The effects of dust selective absorption on the ionization structure are investigated by means of dust opacities measured in laboratory experiments. The infrared spectrum emitted by dust present in both ionized and neutral circumstellar regions is calculated for various choices of the model parameters. The IR dust continuum emission in planetary nebula NGC 7027 is also modelled on the basis of a possible evolutionary scenario for carbon dust grains. Our results provide evidence that by means of UV dust processing it is possible to account for most of the spectral distribution of carbon-rich planetary nebulae. However, non-equilibrium emission is needed to explain near-IR bands and part of the underlying continuum.