Spectroscopy of corannulene cations in helium nanodroplets
  Helium tagging in action spectroscopy is an efficient method for measuring
the absorption spectrum of complex molecular ions with minimal perturbations to
the gas phase spectrum. We have used superfluid helium nanodroplets doped with
corannulene to prepare cations of these molecules complexed with different
numbers of He atoms. In total we identify 13 different absorption bands from
corannulene cations between 5500 {\AA} and 6000 {\AA}. The He atoms cause a
small, chemically induced redshift to the band positions of the corannulene
ion. By studying this effect as a function of the number of solvating atoms we
are able to identify the formation of solvation structures that are not visible
in the mass spectrum. The solvation features detected with the action
spectroscopy agree very well with the results of atomistic modeling based on
path-integral molecular dynamics simulations. By additionally doping our He
droplets with D$_2$, we produce protonated corannulene ions. The absorption
spectrum of these ions differs significantly from the case of the radical
cations as the numerous narrow bands are replaced by a broad absorption feature
that spans nearly 2000 {\AA} in width.
