2020/01/06 by Jérémy Bourgalais, Bourgalais, Jérémy, David V. Bekaert +7
Physics and Astronomy · #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies #Astrophysics and Star Formation Studies
paper · pdf · doi:10.48550/arxiv.2001.01632
CircumStellar Envelopes (CSEs) of stars are complex chemical objects for\nwhich theoretical models encounter difficulties in elaborating a comprehensive\noverview of the occurring chemical processes. Along with photodissociation,\nion-neutral reactions and dissociative recombination might play an important\nrole in controlling molecular growth in outer CSEs. The aim of this work is to\nprovide experimental insights into pathways of photochemistry-driven molecular\ngrowth within outer CSEs to draw a more complete picture of the chemical\nprocesses occurring within these molecule-rich environments. A simplified CSE\nenvironment was therefore reproduced in the laboratory through gas-phase\nexperiments exposing relevant gas mixtures to an Extreme UltraViolet (EUV)\nphoton source. This photochemical reactor should ultimately allow us to\ninvestigate chemical processes and their resulting products occurring under\nconditions akin to outer CSEs. We used a recently developed EUV lamp coupled to\nthe APSIS photochemical cell to irradiate CSE relevant gas mixtures of H2,\nCO and N2, at one wavelength, 73.6 nm. The detection and identification of\nchemical species in the photochemical reactor was achieved through in-situ mass\nspectrometry analysis of neutral and cationic molecules. We find that exposing\nCO-N2-H2 gas mixtures to EUV photons at 73.6 nm induces photochemical\nreactions that yield the formation of complex, neutral and ionic species. Our\nwork shows that N2H+ can be formed through photochemistry along with\nhighly oxygenated ion molecules like HCO+ in CSE environments. We also\nobserve neutral N-rich organic species including triazole and aromatic\nmolecules. These results confirm the suitability of our experimental setting to\ninvestigate photochemical reactions and provide fundamental insights into the\nmechanisms of molecular growth in the outer CSEs.\n