  This paper calls attention to the relevance of Raman scattering by atomic
hydrogen to three optical and near/mid-infrared spectral features of HI clouds:
extended red emission (ERE), diffuse interstellar bands (DIBs), and the
unidentified infrared bands (UIBs). DIBs, ERE, and UIBs are observed
predominantly at the edge of HI clouds, are manifestly related, and remain
poorly understood. Their salient properties correspond to two major
characteristics of HI Raman scattering: unusual line broadenings and a
concentration of the Raman scattered ultraviolet continuum in the vicinity of
hydrogen's optical and infrared transitions. Raman scattering by atomic
hydrogen has now been detected in several object classes where the spectral
features are observed, and I argue that it can account for all three features.
I further identify three factors that condition observation of Raman scattering
in HI clouds, and thus of DIBs, ERE, and UIBs: the hardness of the radiation
field, interstellar dust extinction, and the geometry of the observation. The
geometry determines whether complete forward scattering, yielding DIBs, or
scattering at large angles, yielding ERE in the vicinity of H{\alpha} and UIBs
in the infrared spectrum, will be observed. ERE results from Raman scattering
of photons near Ly\b{eta} and UIBs from excitation of hydrogen atoms close to
the ionization limit. DIBs, ERE, UIBs are thus different facets of the same
interstellar phenomenon: Raman scattering by atomic hydrogen.
