Investigation of HNCO isomer formation in ice mantles by UV and thermal processing: An experimental approach

Journal Article · Tue Jun 10 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/788/1/19· OSTI ID:22356690

Jiménez-Escobar, A.; Giuliano, B. M.; Caro, G. M. Muñoz; Cernicharo, J. ^[1]

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1. Centro de Astrobiología, INTA-CSIC, Carretera de Ajalvir, km 4, Torrejón de Ardoz, E-28850 Madrid (Spain)

Current gas-phase models do not account for the abundances of HNCO isomers detected in various environments, suggesting their formation in icy grain mantles. We attempted to study a formation channel of HNCO and its possible isomers by vacuum-UV photoprocessing of interstellar ice analogs containing H{sub 2}O, NH{sub 3}, CO, HCN, CH{sub 3}OH, CH{sub 4}, and N{sub 2} followed by warm-up under astrophysically relevant conditions. Only the H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ice mixtures led to the production of HNCO species. The possible isomerization of HNCO to its higher energy tautomers following irradiation or due to ice warm-up has been scrutinized. The photochemistry and thermal chemistry of H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ices were simulated using the Interstellar Astrochemistry Chamber, a state-of-the-art ultra-high-vacuum setup. The ice was monitored in situ by Fourier transform mid-infrared spectroscopy in transmittance. A quadrupole mass spectrometer detected the desorption of the molecules in the gas phase. UV photoprocessing of H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ices lead to the formation of OCN{sup –} as a main product in the solid state and a minor amount of HNCO. The second isomer HOCN has been tentatively identified. Despite its low efficiency, the formation of HNCO and the HOCN isomers by UV photoprocessing of realistic simulated ice mantles might explain the observed abundances of these species in photodissociation regions, hot cores, and dark clouds.

• OSTI ID: 22356690
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 788; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION SPECTROSCOPY
ABUNDANCE
ASTROPHYSICS
CARBON MONOXIDE
DESORPTION
DISSOCIATION
FOURIER TRANSFORMATION
HYDROCYANIC ACID
INFRARED SPECTRA
IRRADIATION
ISOMERIZATION
MASS SPECTROMETERS
METHANE
METHANOL
MOLECULES
PHOTOCHEMISTRY
PHOTOLYSIS
SIMULATION
ULTRAVIOLET RADIATION
WATER