The following document lists the file abstract/LALLAMAN_PAH_EVOL.abs
from catalogue VI/111.
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We propose to probe the evolution of interstellar carbon from the molecular to the particle phase by searching for the infrared emission signatures of specific polycyclic aromatic hydrocarbon (PAH) molecules and various forms of amorphous carbon in carbon-rich objects which span the evolutionary range from late carbon stars to molecular clouds. We propose to achieve this goal by measuring the 5-9 micron spectra of these objects, the spectral region which is most diagnostic of these materials and the region in which they emit most strongly. This will provide direct insight into the processes of carbon nucleation and growth in circumstellar shells and the interstellar medium. This is the opportune time for this project. We propose to obtain spectra with ISO of sufficient quality to detect the spectral substructure which must be present superimposed on the larger spectral features already observed in emission from these objects. With our lab data we will be able to interpret these spectra in terms of which molecules and amorphous carbon structures are actually present in these objects and determine their abundances. With data of the quality expected from ISO, it will finally be possible to probe directly into the process of carbon nucleation and growth, gaining insight into the evolution of carbon from its molecular form to larger amorphous particles, and understand which species are associated with each type of object.