  The Cassini Mission has greatly improved our understanding of the dynamics
and chemical processes occurring in Titan's atmosphere. It has also provided us
with more insight into the formation of the aerosols in the upper atmospheric
layers. However, the chemical composition and mechanisms leading to their
formation were out of reach for the instruments onboard Cassini. In this
context, it is deemed necessary to apply and exploit laboratory simulations to
better understand the chemical reactivity occurring in the gas phase of
Titan-like conditions. In the present work, we report gas phase results
obtained from a plasma discharge simulating the chemical processes in Titan's
ionosphere. We use the PAMPRE cold dusty plasma experiment with an N2-CH4
gaseous mixture under controlled pressure and gas influx. An internal cryogenic
trap has been developed to accumulate the gas products during their production
and facilitate their detection. The cryogenic trap condenses the gas-phase
precursors while they are forming, so that aerosols are no longer observed
during the 2h plasma discharge. We focus mainly on neutral products NH3, HCN,
C2H2 and C2H4. The latter are identified and quantified by in situ mass
spectrometry and infrared spectroscopy. We present here results from this
experiment with mixing ratios of 90-10% and 99-1% N2-CH4, covering the range of
methane concentrations encountered in Titan's ionosphere. We also detect in
situ heavy molecules (C7). In particular, we show the role of ethylene and
other volatiles as key solid-phase precursors.
