On the diffuse interstellar bands

Abstract

The problem of the diffuse interstellar bands is considered from a spectroscopic viewpoint. A partial decomposition of the astrophysical spectrum based on the grouping of some of the bands into families is discussed with particular reference to ‘diffuse bands’ observed in emission from the Red Rectangle nebula. The level of consistency between currently available laboratory spectroscopic data for chlorin (and related molecules) and part of the astrophysical spectrum is assessed. Some speculative comments on extended red emission from nebulae are presented.