Acrylonitrile characterization and high energetic photochemistry at Titan temperatures

• Published in: Icarus (New York, N.Y. 1962) Vol. 270; pp. 435 - 442
• Main Authors: Toumi, A., Piétri, N., Chiavassa, T., Couturier-Tamburelli, I.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.05.2016; Elsevier
• Subjects: Acrylonitriles; Chemical Sciences; Crystal structure; Heating; Hydrogen; Hydrogen cyanide; Ices, IR Spectroscopy; Lamps; Photochemistry; Surface temperature; Titan; Ultraviolet; Titan; Photochemistry; Ices, IR Spectroscopy
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2014.10.042

•Spectroscopic and photochemical analysis of processes during irradiation of acrylonitrile ice.•The branching ratio of each pathway has been calculated for the different temperatures.•Acrylonitrile, HCN and HC3N (A νCN) band strengths are respectively: 3.98, 1.38 and 2.92×10−18 cmmolecule−1.•The desorption’s energy of acrylonitrile was determined to be around 35 kJmol−1.•Acrylonitrile shows a phase transition at ∼94K (closed to Titan temperature). Laboratory infrared spectra of amorphous and crystalline acrylonitrile (C2H3CN) ices were recorded between 4000 and 650cm−1. Heating up the acrylonitrile sample to 160K shows details on the transition between amorphous and crystalline ice at ∼94K. This molecule can be used as an indicator of the surface temperature of Titan since it is known also to be ∼94K. The desorption energy of acrylonitrile was determined using two methods (IRTF and mass spectrometries) to be around 35kJmol−1. Solid phase acrylonitrile was irradiated with vacuum ultraviolet (VUV) light at low temperatures (20, 70, 95 and 130K) using a microwave-discharge hydrogen flow lamp. Isoacrylonitrile, cyanoacetylene (HC3N), isocyanoacetylene (HC2NC), acetylene (C2H2) and hydrogen cyanide (HCN) were identified as photoproducts by using FTIR spectroscopy. The branching ratio of each pathway has been calculated for the different temperatures. We have estimated the acrylonitrile, HCN and HC3N νCN stretching band strengths to be respectively A=3.98×10-18, A=1.38×10-18 and A=2.92×10-18cmmolecule-1.