Carbon Chains and the Diffuse Interstellar Bands

Abstract

It is shown that a stable population of long carbon chains and large planar rings is maintained by C⁺ insertion, photocleavage, and spontaneous isomerization in the diffuse interstellar gas. Chains with ~20–30 atoms are synthesized at about the right abundance to account for the diffuse bands, and it is suggested that these and derivative acetylenic rings comparable in size or slightly larger are an important, possibly dominant, component of large molecules in the diffuse gas. It is Further suggested that in a slower subordinate cycle spontaneous isomerization further converts some of the larger planar rings to fullerenes, which then add carbon and possibly other atoms to form even larger molecules and amorphous grains which are recycled only very slowly via grain-grain collisions and supernova shocks.