論文

2020年2月

N-14/N-15 Isotopic Ratio in CH3CN of Titan's Atmosphere Measured with ALMA

ASTROPHYSICAL JOURNAL
  • Takahiro Iino
  • ,
  • Hideo Sagawa
  • ,
  • Takashi Tsukagoshi

890
2
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.3847/1538-4357/ab66b0
出版者・発行元
IOP PUBLISHING LTD

The nitriles present in the atmosphere of Titan can be expected to exhibit different N-14/N-15 values depending on their production processes, primarily because of the various N-2 dissociation processes induced by different sources such as ultraviolet radiation, magnetospheric electrons, and Galactic cosmic rays. For CH3CN, one photochemical model predicted a N-14/N-15 value of 120-130 in the lower stratosphere. This is much higher than that for HCN and HC3N, similar to 67-94. By analyzing archival data obtained by the Atacama Large Millimeter/submillimeter Array, we successfully detected submillimeter rotational transitions of (CH3CN)-N-15 (J = 19-18) located in the 338 GHz band in Titan's atmospheric spectra. By comparing those observations with the simultaneously observed CH3CN (J = 19-18) lines in the 349 GHz band, which probe from 160 to similar to 400 km altitude, we then derived N-14/N-15 in CH3CN as 125(-44)(+145) . Although the range of the derived value shows insufficient accuracy due to limitations on data quality, the best-fit value suggests that N-14/N-15 for CH3CN is higher than values that have previously been observed and theoretically predicted for HCN and HC3N. This may be explained by the different N-2 dissociation sources according to altitude, as suggested by a recent photochemical model.


リンク情報
DOI
https://doi.org/10.3847/1538-4357/ab66b0
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000522100700004&DestApp=WOS_CPL

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