Perturbation of the Surface of Amorphous Solid Water by the Adsorption
  of Polycyclic Aromatic Hydrocarbons
  This joint theoretical and experimental study establishes that the adsorption
of polycyclic aromatic hydrocarbons (PAHs) onto the amorphous ice surface
provokes a broadening and redshift of the "dangling" OH (dOH) ice spectral
feature, the redshift increasing with PAH size up to $\sim$ 85~cm$^{-1}$. It
also reveals that, in certain interaction configurations, adsorption induces
substantial reorganisation of the hydrogen-bonding network at the ice surface.
Comparison with experiments validates the novel theoretical methodology relying
on the density functional based tight binding approach, which offers a
compromise between system size and accuracy enabling a wide sampling of surface
structures. Applied in an astrophysical context, this study suggests that
widening of the dOH feature by adsorption of aromatic molecules could explain
its absence heretofore in observational ice spectra, offering hope that future
missions with higher sensitivity will verify its presence or absence in dense
regions.
