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Title: | Formation of S-bearing Species by VUV/EUV Irradiation of H<SUB>2</SUB>S-containing Ice Mixtures: Photon Energy and Carbon Source Effects | Authors: | Chen, Y. -J. Juang, K. -J. Nuevo, M. JIMENEZ ESCOBAR, Antonio Muñoz Caro, G. M. Qiu, J. -M. Chu, C. -C. Yih, T. -S. Wu, C. -Y. R. Fung, H. -S. Ip, W. -H. |
Issue Date: | 2015 | Journal: | THE ASTROPHYSICAL JOURNAL | Number: | 798 | Issue: | 2 | First Page: | 80 | Abstract: | Carbonyl sulfide (OCS) is a key molecule in astrobiology that acts as a catalyst in peptide synthesis by coupling amino acids. Experimental studies suggest that hydrogen sulfide (H<SUB>2</SUB>S), a precursor of OCS, could be present in astrophysical environments. In the present study, we used a microwave-discharge hydrogen-flow lamp, simulating the interstellar UV field, and a monochromatic synchrotron light beam to irradiate CO:H<SUB>2</SUB>S and CO<SUB>2</SUB>:H<SUB>2</SUB>S ice mixtures at 14 K with vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) photons in order to study the effect of the photon energy and carbon source on the formation mechanisms and production yields of S-containing products (CS<SUB>2</SUB>, OCS, SO<SUB>2</SUB>, etc.). Results show that (1) the photo-induced OCS production efficiency in CO:H<SUB>2</SUB>S ice mixtures is higher than that of CO<SUB>2</SUB>:H<SUB>2</SUB>S ice mixtures; (2) a lower concentration of H<SUB>2</SUB>S enhances the production efficiency of OCS in both ice mixtures; and (3) the formation pathways of CS<SUB>2</SUB> differ significantly upon VUV and EUV irradiations. Furthermore, CS<SUB>2</SUB> was produced only after VUV photoprocessing of CO:H<SUB>2</SUB>S ices, while the VUV-induced production of SO<SUB>2</SUB> occurred only in CO<SUB>2</SUB>:H<SUB>2</SUB>S ice mixtures. More generally, the production yields of OCS, H<SUB>2</SUB>S<SUB>2</SUB>, and CS<SUB>2</SUB> were studied as a function of the irradiation photon energy. Heavy S-bearing compounds were also observed using mass spectrometry during the warm-up of VUV/EUV-irradiated CO:H<SUB>2</SUB>S ice mixtures. The presence of S-polymers in dust grains may account for the missing sulfur in dense clouds and circumstellar environments. | URI: | http://hdl.handle.net/20.500.12386/23410 | URL: | https://iopscience.iop.org/article/10.1088/0004-637X/798/2/80 | ISSN: | 0004-637X | DOI: | 10.1088/0004-637X/798/2/80 | Bibcode ADS: | 2015ApJ...798...80C | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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Chen_2015_ApJ_798_80.pdf | PDF editoriale | 1.46 MB | Adobe PDF | View/Open |
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