  The role of polycyclic aromatic hydrocarbons (PAH) and Nitrogen containing
PAH (PANH) as intermediates of aerosol production in the atmosphere of Titan
has been a subject of controversy for a long time. An analysis of the
atmospheric emission band observed by the Visible and Infrared Mapping
Spectrometer (VIMS) at 3.28 micrometer suggests the presence of neutral
polycyclic aromatic species in the upper atmosphere of Titan. These molecules
are seen as the counter part of negative and positive aromatics ions suspected
by the Plasma Spectrometer onboard the Cassini spacecraft, but the low
resolution of the instrument hinders any molecular speciation.
  In this work we investigate the specific aromatic content of Titan's
atmospheric aerosols through laboratory simulations. We report here the
selective detection of aromatic compounds in tholins, Titan's aerosol
analogues, produced with a capacitively coupled plasma in a N2:CH4 95:5 gas
mixture. For this purpose, Two-Step Laser Desorption Ionization Time-of-Flight
Mass Spectrometry (L2DI-TOF-MS) technique is used to analyze the so produced
analogues. This analytical technique is based on the ionization of molecules by
Resonance Enhanced Multi-Photon Ionization (REMPI) using a {\lambda}=248 nm
wavelength laser which is selective for aromatic species. This allows for the
selective identification of compounds having at least one aromatic ring. Our
experiments show that tholins contain a trace amount of small PAHs with one to
three aromatic rings. Nitrogen containing PAHs (PANHs) are also detected as
constituents of tholins. Molecules relevant to astrobiology are detected as is
the case of the substituted DNA base adenine.
