Interpreting the subtle spectral variations of the 11.2 and 12.7 {\mu}m
  polycyclic aromatic hydrocarbon bands
  We report new properties of the 11 and 12.7 {\mu}m emission complexes of
polycyclic aromatic hydrocarbons (PAHs) by applying a Gaussian-based
decomposition technique. Using high-resolution \textit{Spitzer} Space Telescope
data, we study in detail the spectral and spatial characteristics of the 11 and
12.7 {\mu}m emission bands in maps of reflection nebulae NGC 7023 and NGC 2023
(North and South) and the star-forming region M17. Profile variations are
observed in both the 11 and 12.7 {\mu}m emission bands. We identify a neutral
contribution to the traditional 11.0 {\mu}m PAH band and a cationic
contribution to the traditional 11.2 {\mu}m band, the latter of which affects
the PAH class of the 11.2 {\mu}m emission in our sample. The peak variations of
the 12.7 {\mu}m complex are explained by the competition between two underlying
blended components. The spatial distributions of these components link them to
cations and neutrals. We conclude that the 12.7 {\mu}m emission originates in
both neutral and cationic PAHs, lending support to the use of the 12.7/11.2
intensity ratio as a charge proxy.
