{CircumStellar Envelopes (CSEs) of stars are complex chemical objects for
which theoretical models encounter difficulties in elaborating a comprehensive
overview of the occurring chemical processes. Along with photodissociation,
ion-neutral reactions and dissociative recombination might play an important
role in controlling molecular growth in outer CSEs. The aim of this work is to
provide experimental insights into pathways of photochemistry-driven molecular
growth within outer CSEs to draw a more complete picture of the chemical
processes occurring within these molecule-rich environments. A simplified CSE
environment was therefore reproduced in the laboratory through gas-phase
experiments exposing relevant gas mixtures to an Extreme UltraViolet (EUV)
photon source. This photochemical reactor should ultimately allow us to
investigate chemical processes and their resulting products occurring under
conditions akin to outer CSEs. We used a recently developed EUV lamp coupled to
the APSIS photochemical cell to irradiate CSE relevant gas mixtures of H2,
CO and N2, at one wavelength, 73.6 nm. The detection and identification of
chemical species in the photochemical reactor was achieved through in-situ mass
spectrometry analysis of neutral and cationic molecules. We find that exposing
CO-N2-H2 gas mixtures to EUV photons at 73.6 nm induces photochemical
reactions that yield the formation of complex, neutral and ionic species. Our
work shows that N2H+ can be formed through photochemistry along with
highly oxygenated ion molecules like HCO+ in CSE environments. We also
observe neutral N-rich organic species including triazole and aromatic
molecules. These results confirm the suitability of our experimental setting to
investigate photochemical reactions and provide fundamental insights into the
mechanisms of molecular growth in the outer CSEs