Organic molecules and the diffuse interstellar bands

The paper presents a short history of the interstellar molecules in astrophysics: from the simple, two-atom ones, discovered in late thirties, to quite complicated species, observed recently. The latter are now the most likely the carriers of the diffuse interstellar bands which remain unidentified since 1922. The observational properties of interstellar absorption spectra are briefly described with a special emphasis on the new high resolution profiles of diffuse bands which can allow their identification if matching laboratory spectra of complicated, carbon-bearing molecules determined in the gas phase. The proposed diffuse band carriers are also discussed and their spectra compared with those observed. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.