  The detection of fullerene molecules in a variety of astrophysical
environments suggests that smaller dehydrogenated carbon molecules may also be
present in these sources. One of these is planar C24 which has been shown to be
more stable than the cage fullerene with the same number of carbon atoms. To
facilitate searches for C24 and some simple derivatives we have calculated
infrared spectra for these molecules using first principles density functional
techniques (DFT). Infrared spectra are also presented for several novel carbon
cage molecules formed from dehydrogenated polycyclic aromatic hydrocarbon
molecules. Infrared spectra of a number of these molecules are quite
distinctive and we discuss the possibility of detecting these species in the
presence of C60 and other fullerenes.
