  The recent influx of high-quality infrared spectroscopic data has prompted an
extensive reassessment of various laboratory models in comparison with the
observed UIBs (Unidentified Infrared Bands). As a result, significant
modifications were brought to the original paradigms. The focus here is on the
correction of the coal model, characterized by: 1) a shift towards less
aromatic materials of the same family (kerogens; the composition, structure and
IR spectrum of these materials are extensively documented in the geology
literature); 2) the introduction of a new excitation mechanism
(chemiluminescence), based on the capture of hydrogen atoms by carbonaceous
dust. The fundamental characters of this model, viz. chemical and structural
disorder, and diversity of chemical bondings, naturally point to ways of
further tailoring, in order to fit particular observations more closely.
