Origin of diffuse interstellar bands: spectroscopic studies of their possible carriers

The results of astrophysical observations that provide evidence for the mol ecular origin of the diffuse interstellar bands (DIBs) are reviewed. It is established that molecular systems with a linear, planar or spherical carbo n skeleton are good candidates as DIB carriers, and laboratory spectroscopi c data concerning such systems are discussed. The characteristic features o f the electronic spectra of fullerenes, polycyclic aromatic hydrocarbons, a nd of linear carbon chains and their ions are found to be consistent with t he principal spectroscopic features of DIBs. Analysis of the astrophysical electronic spectra of several simple molecules that have so far been assign ed indicates that polar molecules should be easier to detect in this way th an those without a permanent electric dipole moment. (C) 2000 Elsevier Scie nce B.V. All rights reserved.