Vacuum ultraviolet of hydrogenated amorphous carbons II. Small hydrocarbons production in Photon Dominated Regions

• Published in: Astronomy and astrophysics (Berlin) Vol. 584; p. A123
• Main Authors: Alata, I, Jallat, A, Gavilan, L, Chabot, M, Cruz-Diaz, G A, Caro, G M Munoz, Beroff, K, Dartois, E
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.12.2015
• Subjects: Astrophysics; Carbon; Exposure; Hydrocarbons; Interstellar matter; Photolysis; Photons; Sciences of the Universe; Time; Ultraviolet; molecular processes; photon-dominated region (PDR); ultraviolet: ISM; astrochemistry; methods: laboratory: solid state; ISM: abundances
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361/201526368

Hydrogenated amorphous carbons (a-C :H) are a major component of the carbonaceous solids present in the interstellar medium. The production and existence of these grains is connected in particular with the balance between their photolysis, radiolysis, and hydrogenation. We perform photolytic experiments on laboratory produced interstellar a-C :H analogues to monitor and quantify the release of species and compare to relevant observations in the interstellar medium. Hydrogenated amorphous carbon analogues at low temperature are exposed to ultraviolet (UV) photons, under ultrahigh vacuum conditions. We implement the laboratory measured yields for the released species in a time dependent model to investigate the effect of the UV photon irradiation of hydrogenated amorphous carbons in a photon dominated region, and estimate the associated time scale. The UV photolysis of hydrogenated amorphous carbons leads to the production of H2 molecules and small hydrocarbons. This time scale is consistent with the estimated advection front of a photon dominated region, which replenishes it with freshly exposed material.