On the relationship between the continuum of interstellar extinction
  curves, the 2200 \AA\ bump, and the diffuse interstellar bands
  A previous article argued that the antagonism between sight-lines with and
without a bump at 2200 \AA\ disappears, and that the observed properties of
interstellar extinction can be globally understood, if it is accepted that
scattered starlight contaminates the observed spectrum of reddened stars. The
present paper develops this new paradigm by providing a better understanding of
the characteristics of this scattered light. It further examines the
consequences of this revision of interstellar extinction theory for
interpreting the 2200 \AA\ bump and the diffuse interstellar bands (DIBs). Two
implications are worth noting: (1) the effect of interstellar extinction on
cosmic distance estimations needs to be reconsidered; (2) it is unnecessary to
invoke hypothetical particles, such as Poly Aromatic Hydrogenated molecules
(PAHs), to explain the peculiarities of interstellar extinction. Hydrogen, by
far the most abundant constituent of interstellar clouds, should alone account
for the three major features of interstellar extinction: the departure of the
continuum from linearity, the bump, and the DIBs.
