2017/09/26 by R. Martín-Doménech, R. Martin-Domenech, G. A. Cruz-Díaz +3 · 27 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Adsorption #Analytical Chemistry (journal) #Astrochemistry #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Atomic physics #Chemistry #Desorption #Fluence #Interstellar ice #Interstellar medium #Irradiation #Mass spectrometry #Molecular Spectroscopy and Structure #Molecule #Nuclear physics #Photochemistry #Physical chemistry #Physics #Quadrupole mass analyzer #astro-ph.EP #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stx2510
published in Monthly Notices of the Royal Astronomical Society 473(2), 2575-2582 (Oxford University Press)
openalex publication_date 2017/09/26 · arxiv created 2017/10/17 · arxiv updated 2017/11/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Ice mantles detected on the surface of dust grains towards the coldest regions of the interstellar medium can be photoprocessed by the secondary ultraviolet (UV) field present in dense cloud interiors. In this work, we present UV-irradiation experiments under astrophysically relevant conditions of pure NH3 ice samples in an ultra-high vacuum chamber where solid samples were deposited on to a substrate at 8 K. The ice analogues were subsequently photoprocessed with a microwave-discharged hydrogen-flow lamp. The induced radiation and photochemistry led to the production of H2, N2 and N2H4. In addition, photodesorption to the gas phase of the original ice component, NH3, and two of the three detected photoproducts, H2 and N2, was observed thanks to a quadrupole mass spectrometer (QMS). Calibration of the QMS allowed quantification of the photodesorption yields, leading to Ypd (NH3) = 2.1|+2.1-1.0| × 10−3|\frac\rm molecules\rm incident photon|, which remained constant during the whole experiments, while photodesorption of H2 and N2 increased with fluence, pointing towards an indirect photodesorption mechanism involving energy transfer for these species. Photodesorption yield of N2 molecules after a fluence equivalent to that experienced by ice mantles in space was similar to that of the NH3 molecules (Ypd (N2) = 1.7|+1.7-0.9| × 10−3|\frac\rm molecules\rm incident photon|).