SIMPLE LINEAR POLYCYCLIC AROMATIC HYDROCARBON MOLECULES AND THE INFRARED-EMISSION FEATURES - MOTHBALLS IN THE ORION RIDGE

We show that the IR emission spectrum in objects such as the Orion ridge is compatible with the presence of two- to five-ring linear PAH species in amorphous carbons; specifically the derivatives of naphthalene, anthracene, tetracene, and perhaps pentacene. An origin for these molecules in carbon dust is indicated and is consistent with the structure of laboratory hydrogenated amorphous carbons (a-C : H). Benzene and the simplest aromatic ring molecule, cyclopropenylidene, may be observable in sources which show the UIR emission features.